Linux-Fsdevel Archive on lore.kernel.org
 help / color / Atom feed
* [PATCH v2] debugfs: Check module state before warning in {full/open}_proxy_open()
@ 2020-02-06  6:47 Taehee Yoo
  2020-02-10 21:40 ` Greg KH
  0 siblings, 1 reply; 8+ messages in thread
From: Taehee Yoo @ 2020-02-06  6:47 UTC (permalink / raw)
  To: gregkh, rafael, linux-fsdevel; +Cc: ap420073

When the module is being removed, the module state is set to
MODULE_STATE_GOING. At this point, try_module_get() fails.
And when {full/open}_proxy_open() is being called,
it calls try_module_get() to try to hold module reference count.
If it fails, it warns about the possibility of debugfs file leak.

If {full/open}_proxy_open() is called while the module is being removed,
it fails to hold the module.
So, It warns about debugfs file leak. But it is not the debugfs file
leak case. So, this patch just adds module state checking routine
in the {full/open}_proxy_open().

Test commands:
    #SHELL1
    while :
    do
        modprobe netdevsim
        echo 1 > /sys/bus/netdevsim/new_device
        modprobe -rv netdevsim
    done

    #SHELL2
    while :
    do
        cat /sys/kernel/debug/netdevsim/netdevsim1/ports/0/ipsec
    done

Splat looks like:
[  298.766738][T14664] debugfs file owner did not clean up at exit: ipsec
[  298.766766][T14664] WARNING: CPU: 2 PID: 14664 at fs/debugfs/file.c:312 full_proxy_open+0x10f/0x650
[  298.768595][T14664] Modules linked in: netdevsim(-) openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 n][  298.771343][T14664] CPU: 2 PID: 14664 Comm: cat Tainted: G        W         5.5.0+ #1
[  298.772373][T14664] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[  298.773545][T14664] RIP: 0010:full_proxy_open+0x10f/0x650
[  298.774247][T14664] Code: 48 c1 ea 03 80 3c 02 00 0f 85 c1 04 00 00 49 8b 3c 24 e8 e4 b5 78 ff 84 c0 75 2d 4c 89 ee 48
[  298.776782][T14664] RSP: 0018:ffff88805b7df9b8 EFLAGS: 00010282[  298.777583][T14664] RAX: dffffc0000000008 RBX: ffff8880511725c0 RCX: 0000000000000000
[  298.778610][T14664] RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8880540c5c14
[  298.779637][T14664] RBP: 0000000000000000 R08: fffffbfff15235ad R09: 0000000000000000
[  298.780664][T14664] R10: 0000000000000001 R11: 0000000000000000 R12: ffffffffc06b5000
[  298.781702][T14664] R13: ffff88804c234a88 R14: ffff88804c22dd00 R15: ffffffff8a1b5660
[  298.782722][T14664] FS:  00007fafa13a8540(0000) GS:ffff88806c800000(0000) knlGS:0000000000000000
[  298.783845][T14664] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  298.784672][T14664] CR2: 00007fafa0e9cd10 CR3: 000000004b286005 CR4: 00000000000606e0
[  298.785739][T14664] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  298.786769][T14664] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  298.787785][T14664] Call Trace:
[  298.788237][T14664]  do_dentry_open+0x63c/0xf50
[  298.788872][T14664]  ? open_proxy_open+0x270/0x270
[  298.789524][T14664]  ? __x64_sys_fchdir+0x180/0x180
[  298.790169][T14664]  ? inode_permission+0x65/0x390
[  298.790832][T14664]  path_openat+0xc45/0x2680
[  298.791425][T14664]  ? save_stack+0x69/0x80
[  298.791988][T14664]  ? save_stack+0x19/0x80
[  298.792544][T14664]  ? path_mountpoint+0x2e0/0x2e0
[  298.793233][T14664]  ? check_chain_key+0x236/0x5d0
[  298.793910][T14664]  ? sched_clock_cpu+0x18/0x170
[  298.794527][T14664]  ? find_held_lock+0x39/0x1d0
[  298.795153][T14664]  do_filp_open+0x16a/0x260
[ ... ]

Fixes: 9fd4dcece43a ("debugfs: prevent access to possibly dead file_operations at file open")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
---

v1 -> v2:
 - Fix compile error

 fs/debugfs/file.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 634b09d18b77..e3075389fba0 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -175,8 +175,13 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
 	if (r)
 		goto out;
 
-	real_fops = fops_get(real_fops);
-	if (!real_fops) {
+	if (!fops_get(real_fops)) {
+#ifdef MODULE
+		if (real_fops->owner &&
+		    real_fops->owner->state == MODULE_STATE_GOING)
+			goto out;
+#endif
+
 		/* Huh? Module did not clean up after itself at exit? */
 		WARN(1, "debugfs file owner did not clean up at exit: %pd",
 			dentry);
@@ -305,8 +310,13 @@ static int full_proxy_open(struct inode *inode, struct file *filp)
 	if (r)
 		goto out;
 
-	real_fops = fops_get(real_fops);
-	if (!real_fops) {
+	if (!fops_get(real_fops)) {
+#ifdef MODULE
+		if (real_fops->owner &&
+		    real_fops->owner->state == MODULE_STATE_GOING)
+			goto out;
+#endif
+
 		/* Huh? Module did not cleanup after itself at exit? */
 		WARN(1, "debugfs file owner did not clean up at exit: %pd",
 			dentry);
-- 
2.17.1


^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH v2] debugfs: Check module state before warning in {full/open}_proxy_open()
  2020-02-06  6:47 [PATCH v2] debugfs: Check module state before warning in {full/open}_proxy_open() Taehee Yoo
@ 2020-02-10 21:40 ` Greg KH
  2020-02-11  6:09   ` Taehee Yoo
  0 siblings, 1 reply; 8+ messages in thread
From: Greg KH @ 2020-02-10 21:40 UTC (permalink / raw)
  To: Taehee Yoo; +Cc: rafael, linux-fsdevel

On Thu, Feb 06, 2020 at 06:47:56AM +0000, Taehee Yoo wrote:
> When the module is being removed, the module state is set to
> MODULE_STATE_GOING. At this point, try_module_get() fails.
> And when {full/open}_proxy_open() is being called,
> it calls try_module_get() to try to hold module reference count.
> If it fails, it warns about the possibility of debugfs file leak.
> 
> If {full/open}_proxy_open() is called while the module is being removed,
> it fails to hold the module.
> So, It warns about debugfs file leak. But it is not the debugfs file
> leak case. So, this patch just adds module state checking routine
> in the {full/open}_proxy_open().
> 
> Test commands:
>     #SHELL1
>     while :
>     do
>         modprobe netdevsim
>         echo 1 > /sys/bus/netdevsim/new_device
>         modprobe -rv netdevsim
>     done
> 
>     #SHELL2
>     while :
>     do
>         cat /sys/kernel/debug/netdevsim/netdevsim1/ports/0/ipsec
>     done
> 
> Splat looks like:
> [  298.766738][T14664] debugfs file owner did not clean up at exit: ipsec
> [  298.766766][T14664] WARNING: CPU: 2 PID: 14664 at fs/debugfs/file.c:312 full_proxy_open+0x10f/0x650
> [  298.768595][T14664] Modules linked in: netdevsim(-) openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 n][  298.771343][T14664] CPU: 2 PID: 14664 Comm: cat Tainted: G        W         5.5.0+ #1
> [  298.772373][T14664] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
> [  298.773545][T14664] RIP: 0010:full_proxy_open+0x10f/0x650
> [  298.774247][T14664] Code: 48 c1 ea 03 80 3c 02 00 0f 85 c1 04 00 00 49 8b 3c 24 e8 e4 b5 78 ff 84 c0 75 2d 4c 89 ee 48
> [  298.776782][T14664] RSP: 0018:ffff88805b7df9b8 EFLAGS: 00010282[  298.777583][T14664] RAX: dffffc0000000008 RBX: ffff8880511725c0 RCX: 0000000000000000
> [  298.778610][T14664] RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8880540c5c14
> [  298.779637][T14664] RBP: 0000000000000000 R08: fffffbfff15235ad R09: 0000000000000000
> [  298.780664][T14664] R10: 0000000000000001 R11: 0000000000000000 R12: ffffffffc06b5000
> [  298.781702][T14664] R13: ffff88804c234a88 R14: ffff88804c22dd00 R15: ffffffff8a1b5660
> [  298.782722][T14664] FS:  00007fafa13a8540(0000) GS:ffff88806c800000(0000) knlGS:0000000000000000
> [  298.783845][T14664] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  298.784672][T14664] CR2: 00007fafa0e9cd10 CR3: 000000004b286005 CR4: 00000000000606e0
> [  298.785739][T14664] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [  298.786769][T14664] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [  298.787785][T14664] Call Trace:
> [  298.788237][T14664]  do_dentry_open+0x63c/0xf50
> [  298.788872][T14664]  ? open_proxy_open+0x270/0x270
> [  298.789524][T14664]  ? __x64_sys_fchdir+0x180/0x180
> [  298.790169][T14664]  ? inode_permission+0x65/0x390
> [  298.790832][T14664]  path_openat+0xc45/0x2680
> [  298.791425][T14664]  ? save_stack+0x69/0x80
> [  298.791988][T14664]  ? save_stack+0x19/0x80
> [  298.792544][T14664]  ? path_mountpoint+0x2e0/0x2e0
> [  298.793233][T14664]  ? check_chain_key+0x236/0x5d0
> [  298.793910][T14664]  ? sched_clock_cpu+0x18/0x170
> [  298.794527][T14664]  ? find_held_lock+0x39/0x1d0
> [  298.795153][T14664]  do_filp_open+0x16a/0x260
> [ ... ]
> 
> Fixes: 9fd4dcece43a ("debugfs: prevent access to possibly dead file_operations at file open")
> Reported-by: kbuild test robot <lkp@intel.com>
> Signed-off-by: Taehee Yoo <ap420073@gmail.com>
> ---
> 
> v1 -> v2:
>  - Fix compile error
> 
>  fs/debugfs/file.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> index 634b09d18b77..e3075389fba0 100644
> --- a/fs/debugfs/file.c
> +++ b/fs/debugfs/file.c
> @@ -175,8 +175,13 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
>  	if (r)
>  		goto out;
>  
> -	real_fops = fops_get(real_fops);
> -	if (!real_fops) {
> +	if (!fops_get(real_fops)) {
> +#ifdef MODULE
> +		if (real_fops->owner &&
> +		    real_fops->owner->state == MODULE_STATE_GOING)
> +			goto out;
> +#endif

Why is this in a #ifdef?

The real_fops->owner field will be present if MODULE is not enabled,
right?  Shouldn't this just work the same for that case?

thanks,

greg k-h

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH v2] debugfs: Check module state before warning in {full/open}_proxy_open()
  2020-02-10 21:40 ` Greg KH
@ 2020-02-11  6:09   ` Taehee Yoo
  2020-02-11 12:28     ` Greg KH
  0 siblings, 1 reply; 8+ messages in thread
From: Taehee Yoo @ 2020-02-11  6:09 UTC (permalink / raw)
  To: Greg KH; +Cc: rafael, linux-fsdevel

On Tue, 11 Feb 2020 at 06:40, Greg KH <gregkh@linuxfoundation.org> wrote:
>

Hi Greg,
Thank you for your review!

> On Thu, Feb 06, 2020 at 06:47:56AM +0000, Taehee Yoo wrote:
> > When the module is being removed, the module state is set to
> > MODULE_STATE_GOING. At this point, try_module_get() fails.
> > And when {full/open}_proxy_open() is being called,
> > it calls try_module_get() to try to hold module reference count.
> > If it fails, it warns about the possibility of debugfs file leak.
> >
> > If {full/open}_proxy_open() is called while the module is being removed,
> > it fails to hold the module.
> > So, It warns about debugfs file leak. But it is not the debugfs file
> > leak case. So, this patch just adds module state checking routine
> > in the {full/open}_proxy_open().
> >
> > Test commands:
> >     #SHELL1
> >     while :
> >     do
> >         modprobe netdevsim
> >         echo 1 > /sys/bus/netdevsim/new_device
> >         modprobe -rv netdevsim
> >     done
> >
> >     #SHELL2
> >     while :
> >     do
> >         cat /sys/kernel/debug/netdevsim/netdevsim1/ports/0/ipsec
> >     done
> >
> > Splat looks like:
> > [  298.766738][T14664] debugfs file owner did not clean up at exit: ipsec
> > [  298.766766][T14664] WARNING: CPU: 2 PID: 14664 at fs/debugfs/file.c:312 full_proxy_open+0x10f/0x650
> > [  298.768595][T14664] Modules linked in: netdevsim(-) openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 n][  298.771343][T14664] CPU: 2 PID: 14664 Comm: cat Tainted: G        W         5.5.0+ #1
> > [  298.772373][T14664] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
> > [  298.773545][T14664] RIP: 0010:full_proxy_open+0x10f/0x650
> > [  298.774247][T14664] Code: 48 c1 ea 03 80 3c 02 00 0f 85 c1 04 00 00 49 8b 3c 24 e8 e4 b5 78 ff 84 c0 75 2d 4c 89 ee 48
> > [  298.776782][T14664] RSP: 0018:ffff88805b7df9b8 EFLAGS: 00010282[  298.777583][T14664] RAX: dffffc0000000008 RBX: ffff8880511725c0 RCX: 0000000000000000
> > [  298.778610][T14664] RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8880540c5c14
> > [  298.779637][T14664] RBP: 0000000000000000 R08: fffffbfff15235ad R09: 0000000000000000
> > [  298.780664][T14664] R10: 0000000000000001 R11: 0000000000000000 R12: ffffffffc06b5000
> > [  298.781702][T14664] R13: ffff88804c234a88 R14: ffff88804c22dd00 R15: ffffffff8a1b5660
> > [  298.782722][T14664] FS:  00007fafa13a8540(0000) GS:ffff88806c800000(0000) knlGS:0000000000000000
> > [  298.783845][T14664] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [  298.784672][T14664] CR2: 00007fafa0e9cd10 CR3: 000000004b286005 CR4: 00000000000606e0
> > [  298.785739][T14664] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > [  298.786769][T14664] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > [  298.787785][T14664] Call Trace:
> > [  298.788237][T14664]  do_dentry_open+0x63c/0xf50
> > [  298.788872][T14664]  ? open_proxy_open+0x270/0x270
> > [  298.789524][T14664]  ? __x64_sys_fchdir+0x180/0x180
> > [  298.790169][T14664]  ? inode_permission+0x65/0x390
> > [  298.790832][T14664]  path_openat+0xc45/0x2680
> > [  298.791425][T14664]  ? save_stack+0x69/0x80
> > [  298.791988][T14664]  ? save_stack+0x19/0x80
> > [  298.792544][T14664]  ? path_mountpoint+0x2e0/0x2e0
> > [  298.793233][T14664]  ? check_chain_key+0x236/0x5d0
> > [  298.793910][T14664]  ? sched_clock_cpu+0x18/0x170
> > [  298.794527][T14664]  ? find_held_lock+0x39/0x1d0
> > [  298.795153][T14664]  do_filp_open+0x16a/0x260
> > [ ... ]
> >
> > Fixes: 9fd4dcece43a ("debugfs: prevent access to possibly dead file_operations at file open")
> > Reported-by: kbuild test robot <lkp@intel.com>
> > Signed-off-by: Taehee Yoo <ap420073@gmail.com>
> > ---
> >
> > v1 -> v2:
> >  - Fix compile error
> >
> >  fs/debugfs/file.c | 18 ++++++++++++++----
> >  1 file changed, 14 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> > index 634b09d18b77..e3075389fba0 100644
> > --- a/fs/debugfs/file.c
> > +++ b/fs/debugfs/file.c
> > @@ -175,8 +175,13 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
> >       if (r)
> >               goto out;
> >
> > -     real_fops = fops_get(real_fops);
> > -     if (!real_fops) {
> > +     if (!fops_get(real_fops)) {
> > +#ifdef MODULE
> > +             if (real_fops->owner &&
> > +                 real_fops->owner->state == MODULE_STATE_GOING)
> > +                     goto out;
> > +#endif
>
> Why is this in a #ifdef?
>
> The real_fops->owner field will be present if MODULE is not enabled,
> right?  Shouldn't this just work the same for that case?
>

The reason for the #ifdef is to avoid compile error
MODULE_STATE_GOING is defined if CONFIG_MODULES is enabled.
So, If the #ifdef doesn't exist, compile will errors.
But honestly, I'm not sure whether CONFIG_MODULES should be used
here instead of MODULE or not.

> thanks,
>
> greg k-h

Thank you!
Taehee Yoo

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH v2] debugfs: Check module state before warning in {full/open}_proxy_open()
  2020-02-11  6:09   ` Taehee Yoo
@ 2020-02-11 12:28     ` Greg KH
  2020-02-11 17:18       ` Taehee Yoo
  0 siblings, 1 reply; 8+ messages in thread
From: Greg KH @ 2020-02-11 12:28 UTC (permalink / raw)
  To: Taehee Yoo; +Cc: rafael, linux-fsdevel

On Tue, Feb 11, 2020 at 03:09:13PM +0900, Taehee Yoo wrote:
> On Tue, 11 Feb 2020 at 06:40, Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> 
> Hi Greg,
> Thank you for your review!
> 
> > On Thu, Feb 06, 2020 at 06:47:56AM +0000, Taehee Yoo wrote:
> > > When the module is being removed, the module state is set to
> > > MODULE_STATE_GOING. At this point, try_module_get() fails.
> > > And when {full/open}_proxy_open() is being called,
> > > it calls try_module_get() to try to hold module reference count.
> > > If it fails, it warns about the possibility of debugfs file leak.
> > >
> > > If {full/open}_proxy_open() is called while the module is being removed,
> > > it fails to hold the module.
> > > So, It warns about debugfs file leak. But it is not the debugfs file
> > > leak case. So, this patch just adds module state checking routine
> > > in the {full/open}_proxy_open().
> > >
> > > Test commands:
> > >     #SHELL1
> > >     while :
> > >     do
> > >         modprobe netdevsim
> > >         echo 1 > /sys/bus/netdevsim/new_device
> > >         modprobe -rv netdevsim
> > >     done
> > >
> > >     #SHELL2
> > >     while :
> > >     do
> > >         cat /sys/kernel/debug/netdevsim/netdevsim1/ports/0/ipsec
> > >     done
> > >
> > > Splat looks like:
> > > [  298.766738][T14664] debugfs file owner did not clean up at exit: ipsec
> > > [  298.766766][T14664] WARNING: CPU: 2 PID: 14664 at fs/debugfs/file.c:312 full_proxy_open+0x10f/0x650
> > > [  298.768595][T14664] Modules linked in: netdevsim(-) openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 n][  298.771343][T14664] CPU: 2 PID: 14664 Comm: cat Tainted: G        W         5.5.0+ #1
> > > [  298.772373][T14664] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
> > > [  298.773545][T14664] RIP: 0010:full_proxy_open+0x10f/0x650
> > > [  298.774247][T14664] Code: 48 c1 ea 03 80 3c 02 00 0f 85 c1 04 00 00 49 8b 3c 24 e8 e4 b5 78 ff 84 c0 75 2d 4c 89 ee 48
> > > [  298.776782][T14664] RSP: 0018:ffff88805b7df9b8 EFLAGS: 00010282[  298.777583][T14664] RAX: dffffc0000000008 RBX: ffff8880511725c0 RCX: 0000000000000000
> > > [  298.778610][T14664] RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8880540c5c14
> > > [  298.779637][T14664] RBP: 0000000000000000 R08: fffffbfff15235ad R09: 0000000000000000
> > > [  298.780664][T14664] R10: 0000000000000001 R11: 0000000000000000 R12: ffffffffc06b5000
> > > [  298.781702][T14664] R13: ffff88804c234a88 R14: ffff88804c22dd00 R15: ffffffff8a1b5660
> > > [  298.782722][T14664] FS:  00007fafa13a8540(0000) GS:ffff88806c800000(0000) knlGS:0000000000000000
> > > [  298.783845][T14664] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > [  298.784672][T14664] CR2: 00007fafa0e9cd10 CR3: 000000004b286005 CR4: 00000000000606e0
> > > [  298.785739][T14664] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > [  298.786769][T14664] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > [  298.787785][T14664] Call Trace:
> > > [  298.788237][T14664]  do_dentry_open+0x63c/0xf50
> > > [  298.788872][T14664]  ? open_proxy_open+0x270/0x270
> > > [  298.789524][T14664]  ? __x64_sys_fchdir+0x180/0x180
> > > [  298.790169][T14664]  ? inode_permission+0x65/0x390
> > > [  298.790832][T14664]  path_openat+0xc45/0x2680
> > > [  298.791425][T14664]  ? save_stack+0x69/0x80
> > > [  298.791988][T14664]  ? save_stack+0x19/0x80
> > > [  298.792544][T14664]  ? path_mountpoint+0x2e0/0x2e0
> > > [  298.793233][T14664]  ? check_chain_key+0x236/0x5d0
> > > [  298.793910][T14664]  ? sched_clock_cpu+0x18/0x170
> > > [  298.794527][T14664]  ? find_held_lock+0x39/0x1d0
> > > [  298.795153][T14664]  do_filp_open+0x16a/0x260
> > > [ ... ]
> > >
> > > Fixes: 9fd4dcece43a ("debugfs: prevent access to possibly dead file_operations at file open")
> > > Reported-by: kbuild test robot <lkp@intel.com>
> > > Signed-off-by: Taehee Yoo <ap420073@gmail.com>
> > > ---
> > >
> > > v1 -> v2:
> > >  - Fix compile error
> > >
> > >  fs/debugfs/file.c | 18 ++++++++++++++----
> > >  1 file changed, 14 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> > > index 634b09d18b77..e3075389fba0 100644
> > > --- a/fs/debugfs/file.c
> > > +++ b/fs/debugfs/file.c
> > > @@ -175,8 +175,13 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
> > >       if (r)
> > >               goto out;
> > >
> > > -     real_fops = fops_get(real_fops);
> > > -     if (!real_fops) {
> > > +     if (!fops_get(real_fops)) {
> > > +#ifdef MODULE
> > > +             if (real_fops->owner &&
> > > +                 real_fops->owner->state == MODULE_STATE_GOING)
> > > +                     goto out;
> > > +#endif
> >
> > Why is this in a #ifdef?
> >
> > The real_fops->owner field will be present if MODULE is not enabled,
> > right?  Shouldn't this just work the same for that case?
> >
> 
> The reason for the #ifdef is to avoid compile error
> MODULE_STATE_GOING is defined if CONFIG_MODULES is enabled.

We should fix that in the .h file where that is defined so that we don't
have to mess with stuff like this in a .c file.

> So, If the #ifdef doesn't exist, compile will errors.
> But honestly, I'm not sure whether CONFIG_MODULES should be used
> here instead of MODULE or not.

Neither, #ifdefs shouldn't be in .c files :)

thanks,

greg k-h

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH v2] debugfs: Check module state before warning in {full/open}_proxy_open()
  2020-02-11 12:28     ` Greg KH
@ 2020-02-11 17:18       ` Taehee Yoo
  2020-02-11 18:34         ` Greg KH
  0 siblings, 1 reply; 8+ messages in thread
From: Taehee Yoo @ 2020-02-11 17:18 UTC (permalink / raw)
  To: Greg KH; +Cc: rafael, linux-fsdevel

On Tue, 11 Feb 2020 at 21:28, Greg KH <gregkh@linuxfoundation.org> wrote:
>

Hi Greg!

> On Tue, Feb 11, 2020 at 03:09:13PM +0900, Taehee Yoo wrote:
> > On Tue, 11 Feb 2020 at 06:40, Greg KH <gregkh@linuxfoundation.org> wrote:
> > >
> >
> > Hi Greg,
> > Thank you for your review!
> >
> > > On Thu, Feb 06, 2020 at 06:47:56AM +0000, Taehee Yoo wrote:
> > > > When the module is being removed, the module state is set to
> > > > MODULE_STATE_GOING. At this point, try_module_get() fails.
> > > > And when {full/open}_proxy_open() is being called,
> > > > it calls try_module_get() to try to hold module reference count.
> > > > If it fails, it warns about the possibility of debugfs file leak.
> > > >
> > > > If {full/open}_proxy_open() is called while the module is being removed,
> > > > it fails to hold the module.
> > > > So, It warns about debugfs file leak. But it is not the debugfs file
> > > > leak case. So, this patch just adds module state checking routine
> > > > in the {full/open}_proxy_open().
> > > >
> > > > Test commands:
> > > >     #SHELL1
> > > >     while :
> > > >     do
> > > >         modprobe netdevsim
> > > >         echo 1 > /sys/bus/netdevsim/new_device
> > > >         modprobe -rv netdevsim
> > > >     done
> > > >
> > > >     #SHELL2
> > > >     while :
> > > >     do
> > > >         cat /sys/kernel/debug/netdevsim/netdevsim1/ports/0/ipsec
> > > >     done
> > > >
> > > > Splat looks like:
> > > > [  298.766738][T14664] debugfs file owner did not clean up at exit: ipsec
> > > > [  298.766766][T14664] WARNING: CPU: 2 PID: 14664 at fs/debugfs/file.c:312 full_proxy_open+0x10f/0x650
> > > > [  298.768595][T14664] Modules linked in: netdevsim(-) openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 n][  298.771343][T14664] CPU: 2 PID: 14664 Comm: cat Tainted: G        W         5.5.0+ #1
> > > > [  298.772373][T14664] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
> > > > [  298.773545][T14664] RIP: 0010:full_proxy_open+0x10f/0x650
> > > > [  298.774247][T14664] Code: 48 c1 ea 03 80 3c 02 00 0f 85 c1 04 00 00 49 8b 3c 24 e8 e4 b5 78 ff 84 c0 75 2d 4c 89 ee 48
> > > > [  298.776782][T14664] RSP: 0018:ffff88805b7df9b8 EFLAGS: 00010282[  298.777583][T14664] RAX: dffffc0000000008 RBX: ffff8880511725c0 RCX: 0000000000000000
> > > > [  298.778610][T14664] RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8880540c5c14
> > > > [  298.779637][T14664] RBP: 0000000000000000 R08: fffffbfff15235ad R09: 0000000000000000
> > > > [  298.780664][T14664] R10: 0000000000000001 R11: 0000000000000000 R12: ffffffffc06b5000
> > > > [  298.781702][T14664] R13: ffff88804c234a88 R14: ffff88804c22dd00 R15: ffffffff8a1b5660
> > > > [  298.782722][T14664] FS:  00007fafa13a8540(0000) GS:ffff88806c800000(0000) knlGS:0000000000000000
> > > > [  298.783845][T14664] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > [  298.784672][T14664] CR2: 00007fafa0e9cd10 CR3: 000000004b286005 CR4: 00000000000606e0
> > > > [  298.785739][T14664] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > > [  298.786769][T14664] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > > [  298.787785][T14664] Call Trace:
> > > > [  298.788237][T14664]  do_dentry_open+0x63c/0xf50
> > > > [  298.788872][T14664]  ? open_proxy_open+0x270/0x270
> > > > [  298.789524][T14664]  ? __x64_sys_fchdir+0x180/0x180
> > > > [  298.790169][T14664]  ? inode_permission+0x65/0x390
> > > > [  298.790832][T14664]  path_openat+0xc45/0x2680
> > > > [  298.791425][T14664]  ? save_stack+0x69/0x80
> > > > [  298.791988][T14664]  ? save_stack+0x19/0x80
> > > > [  298.792544][T14664]  ? path_mountpoint+0x2e0/0x2e0
> > > > [  298.793233][T14664]  ? check_chain_key+0x236/0x5d0
> > > > [  298.793910][T14664]  ? sched_clock_cpu+0x18/0x170
> > > > [  298.794527][T14664]  ? find_held_lock+0x39/0x1d0
> > > > [  298.795153][T14664]  do_filp_open+0x16a/0x260
> > > > [ ... ]
> > > >
> > > > Fixes: 9fd4dcece43a ("debugfs: prevent access to possibly dead file_operations at file open")
> > > > Reported-by: kbuild test robot <lkp@intel.com>
> > > > Signed-off-by: Taehee Yoo <ap420073@gmail.com>
> > > > ---
> > > >
> > > > v1 -> v2:
> > > >  - Fix compile error
> > > >
> > > >  fs/debugfs/file.c | 18 ++++++++++++++----
> > > >  1 file changed, 14 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> > > > index 634b09d18b77..e3075389fba0 100644
> > > > --- a/fs/debugfs/file.c
> > > > +++ b/fs/debugfs/file.c
> > > > @@ -175,8 +175,13 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
> > > >       if (r)
> > > >               goto out;
> > > >
> > > > -     real_fops = fops_get(real_fops);
> > > > -     if (!real_fops) {
> > > > +     if (!fops_get(real_fops)) {
> > > > +#ifdef MODULE
> > > > +             if (real_fops->owner &&
> > > > +                 real_fops->owner->state == MODULE_STATE_GOING)
> > > > +                     goto out;
> > > > +#endif
> > >
> > > Why is this in a #ifdef?
> > >
> > > The real_fops->owner field will be present if MODULE is not enabled,
> > > right?  Shouldn't this just work the same for that case?
> > >
> >
> > The reason for the #ifdef is to avoid compile error
> > MODULE_STATE_GOING is defined if CONFIG_MODULES is enabled.
>
> We should fix that in the .h file where that is defined so that we don't
> have to mess with stuff like this in a .c file.
>
> > So, If the #ifdef doesn't exist, compile will errors.
> > But honestly, I'm not sure whether CONFIG_MODULES should be used
> > here instead of MODULE or not.
>
> Neither, #ifdefs shouldn't be in .c files :)
>

Thank you for the review.
I would like to move MODULE_STATE_XXX flags to outside of CONFIG_MODULES.
In addition, I think a new inline function, which checks modules state
would be helpful for this case.
The inline function code would like this.

+static inline bool module_is_going(struct module *mod)
+{
+       return mod->state == MODULE_STATE_GOING;
+}

Thank you!
Taehee Yoo

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH v2] debugfs: Check module state before warning in {full/open}_proxy_open()
  2020-02-11 17:18       ` Taehee Yoo
@ 2020-02-11 18:34         ` Greg KH
  2020-02-12  9:45           ` Taehee Yoo
  0 siblings, 1 reply; 8+ messages in thread
From: Greg KH @ 2020-02-11 18:34 UTC (permalink / raw)
  To: Taehee Yoo; +Cc: rafael, linux-fsdevel

On Wed, Feb 12, 2020 at 02:18:38AM +0900, Taehee Yoo wrote:
> On Tue, 11 Feb 2020 at 21:28, Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> 
> Hi Greg!
> 
> > On Tue, Feb 11, 2020 at 03:09:13PM +0900, Taehee Yoo wrote:
> > > On Tue, 11 Feb 2020 at 06:40, Greg KH <gregkh@linuxfoundation.org> wrote:
> > > >
> > >
> > > Hi Greg,
> > > Thank you for your review!
> > >
> > > > On Thu, Feb 06, 2020 at 06:47:56AM +0000, Taehee Yoo wrote:
> > > > > When the module is being removed, the module state is set to
> > > > > MODULE_STATE_GOING. At this point, try_module_get() fails.
> > > > > And when {full/open}_proxy_open() is being called,
> > > > > it calls try_module_get() to try to hold module reference count.
> > > > > If it fails, it warns about the possibility of debugfs file leak.
> > > > >
> > > > > If {full/open}_proxy_open() is called while the module is being removed,
> > > > > it fails to hold the module.
> > > > > So, It warns about debugfs file leak. But it is not the debugfs file
> > > > > leak case. So, this patch just adds module state checking routine
> > > > > in the {full/open}_proxy_open().
> > > > >
> > > > > Test commands:
> > > > >     #SHELL1
> > > > >     while :
> > > > >     do
> > > > >         modprobe netdevsim
> > > > >         echo 1 > /sys/bus/netdevsim/new_device
> > > > >         modprobe -rv netdevsim
> > > > >     done
> > > > >
> > > > >     #SHELL2
> > > > >     while :
> > > > >     do
> > > > >         cat /sys/kernel/debug/netdevsim/netdevsim1/ports/0/ipsec
> > > > >     done
> > > > >
> > > > > Splat looks like:
> > > > > [  298.766738][T14664] debugfs file owner did not clean up at exit: ipsec
> > > > > [  298.766766][T14664] WARNING: CPU: 2 PID: 14664 at fs/debugfs/file.c:312 full_proxy_open+0x10f/0x650
> > > > > [  298.768595][T14664] Modules linked in: netdevsim(-) openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 n][  298.771343][T14664] CPU: 2 PID: 14664 Comm: cat Tainted: G        W         5.5.0+ #1
> > > > > [  298.772373][T14664] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
> > > > > [  298.773545][T14664] RIP: 0010:full_proxy_open+0x10f/0x650
> > > > > [  298.774247][T14664] Code: 48 c1 ea 03 80 3c 02 00 0f 85 c1 04 00 00 49 8b 3c 24 e8 e4 b5 78 ff 84 c0 75 2d 4c 89 ee 48
> > > > > [  298.776782][T14664] RSP: 0018:ffff88805b7df9b8 EFLAGS: 00010282[  298.777583][T14664] RAX: dffffc0000000008 RBX: ffff8880511725c0 RCX: 0000000000000000
> > > > > [  298.778610][T14664] RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8880540c5c14
> > > > > [  298.779637][T14664] RBP: 0000000000000000 R08: fffffbfff15235ad R09: 0000000000000000
> > > > > [  298.780664][T14664] R10: 0000000000000001 R11: 0000000000000000 R12: ffffffffc06b5000
> > > > > [  298.781702][T14664] R13: ffff88804c234a88 R14: ffff88804c22dd00 R15: ffffffff8a1b5660
> > > > > [  298.782722][T14664] FS:  00007fafa13a8540(0000) GS:ffff88806c800000(0000) knlGS:0000000000000000
> > > > > [  298.783845][T14664] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > > [  298.784672][T14664] CR2: 00007fafa0e9cd10 CR3: 000000004b286005 CR4: 00000000000606e0
> > > > > [  298.785739][T14664] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > > > [  298.786769][T14664] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > > > [  298.787785][T14664] Call Trace:
> > > > > [  298.788237][T14664]  do_dentry_open+0x63c/0xf50
> > > > > [  298.788872][T14664]  ? open_proxy_open+0x270/0x270
> > > > > [  298.789524][T14664]  ? __x64_sys_fchdir+0x180/0x180
> > > > > [  298.790169][T14664]  ? inode_permission+0x65/0x390
> > > > > [  298.790832][T14664]  path_openat+0xc45/0x2680
> > > > > [  298.791425][T14664]  ? save_stack+0x69/0x80
> > > > > [  298.791988][T14664]  ? save_stack+0x19/0x80
> > > > > [  298.792544][T14664]  ? path_mountpoint+0x2e0/0x2e0
> > > > > [  298.793233][T14664]  ? check_chain_key+0x236/0x5d0
> > > > > [  298.793910][T14664]  ? sched_clock_cpu+0x18/0x170
> > > > > [  298.794527][T14664]  ? find_held_lock+0x39/0x1d0
> > > > > [  298.795153][T14664]  do_filp_open+0x16a/0x260
> > > > > [ ... ]
> > > > >
> > > > > Fixes: 9fd4dcece43a ("debugfs: prevent access to possibly dead file_operations at file open")
> > > > > Reported-by: kbuild test robot <lkp@intel.com>
> > > > > Signed-off-by: Taehee Yoo <ap420073@gmail.com>
> > > > > ---
> > > > >
> > > > > v1 -> v2:
> > > > >  - Fix compile error
> > > > >
> > > > >  fs/debugfs/file.c | 18 ++++++++++++++----
> > > > >  1 file changed, 14 insertions(+), 4 deletions(-)
> > > > >
> > > > > diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> > > > > index 634b09d18b77..e3075389fba0 100644
> > > > > --- a/fs/debugfs/file.c
> > > > > +++ b/fs/debugfs/file.c
> > > > > @@ -175,8 +175,13 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
> > > > >       if (r)
> > > > >               goto out;
> > > > >
> > > > > -     real_fops = fops_get(real_fops);
> > > > > -     if (!real_fops) {
> > > > > +     if (!fops_get(real_fops)) {
> > > > > +#ifdef MODULE
> > > > > +             if (real_fops->owner &&
> > > > > +                 real_fops->owner->state == MODULE_STATE_GOING)
> > > > > +                     goto out;
> > > > > +#endif
> > > >
> > > > Why is this in a #ifdef?
> > > >
> > > > The real_fops->owner field will be present if MODULE is not enabled,
> > > > right?  Shouldn't this just work the same for that case?
> > > >
> > >
> > > The reason for the #ifdef is to avoid compile error
> > > MODULE_STATE_GOING is defined if CONFIG_MODULES is enabled.
> >
> > We should fix that in the .h file where that is defined so that we don't
> > have to mess with stuff like this in a .c file.
> >
> > > So, If the #ifdef doesn't exist, compile will errors.
> > > But honestly, I'm not sure whether CONFIG_MODULES should be used
> > > here instead of MODULE or not.
> >
> > Neither, #ifdefs shouldn't be in .c files :)
> >
> 
> Thank you for the review.
> I would like to move MODULE_STATE_XXX flags to outside of CONFIG_MODULES.

That would be good.

> In addition, I think a new inline function, which checks modules state
> would be helpful for this case.
> The inline function code would like this.
> 
> +static inline bool module_is_going(struct module *mod)
> +{
> +       return mod->state == MODULE_STATE_GOING;
> +}

That too would be good, as there are a number of places in the kernel
that could be cleaned up to use this.  Same for MODULE_STATE_COMING,
right?

So a patch series with all of this would be appreciated.

thanks,

greg k-h

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH v2] debugfs: Check module state before warning in {full/open}_proxy_open()
  2020-02-11 18:34         ` Greg KH
@ 2020-02-12  9:45           ` Taehee Yoo
  2020-02-12 15:39             ` Taehee Yoo
  0 siblings, 1 reply; 8+ messages in thread
From: Taehee Yoo @ 2020-02-12  9:45 UTC (permalink / raw)
  To: Greg KH; +Cc: rafael, linux-fsdevel

On Wed, 12 Feb 2020 at 03:34, Greg KH <gregkh@linuxfoundation.org> wrote:
>

Hi Greg!

> On Wed, Feb 12, 2020 at 02:18:38AM +0900, Taehee Yoo wrote:
> > On Tue, 11 Feb 2020 at 21:28, Greg KH <gregkh@linuxfoundation.org> wrote:
> > >
> >
> > Hi Greg!
> >
> > > On Tue, Feb 11, 2020 at 03:09:13PM +0900, Taehee Yoo wrote:
> > > > On Tue, 11 Feb 2020 at 06:40, Greg KH <gregkh@linuxfoundation.org> wrote:
> > > > >
> > > >
> > > > Hi Greg,
> > > > Thank you for your review!
> > > >
> > > > > On Thu, Feb 06, 2020 at 06:47:56AM +0000, Taehee Yoo wrote:
> > > > > > When the module is being removed, the module state is set to
> > > > > > MODULE_STATE_GOING. At this point, try_module_get() fails.
> > > > > > And when {full/open}_proxy_open() is being called,
> > > > > > it calls try_module_get() to try to hold module reference count.
> > > > > > If it fails, it warns about the possibility of debugfs file leak.
> > > > > >
> > > > > > If {full/open}_proxy_open() is called while the module is being removed,
> > > > > > it fails to hold the module.
> > > > > > So, It warns about debugfs file leak. But it is not the debugfs file
> > > > > > leak case. So, this patch just adds module state checking routine
> > > > > > in the {full/open}_proxy_open().
> > > > > >
> > > > > > Test commands:
> > > > > >     #SHELL1
> > > > > >     while :
> > > > > >     do
> > > > > >         modprobe netdevsim
> > > > > >         echo 1 > /sys/bus/netdevsim/new_device
> > > > > >         modprobe -rv netdevsim
> > > > > >     done
> > > > > >
> > > > > >     #SHELL2
> > > > > >     while :
> > > > > >     do
> > > > > >         cat /sys/kernel/debug/netdevsim/netdevsim1/ports/0/ipsec
> > > > > >     done
> > > > > >
> > > > > > Splat looks like:
> > > > > > [  298.766738][T14664] debugfs file owner did not clean up at exit: ipsec
> > > > > > [  298.766766][T14664] WARNING: CPU: 2 PID: 14664 at fs/debugfs/file.c:312 full_proxy_open+0x10f/0x650
> > > > > > [  298.768595][T14664] Modules linked in: netdevsim(-) openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 n][  298.771343][T14664] CPU: 2 PID: 14664 Comm: cat Tainted: G        W         5.5.0+ #1
> > > > > > [  298.772373][T14664] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
> > > > > > [  298.773545][T14664] RIP: 0010:full_proxy_open+0x10f/0x650
> > > > > > [  298.774247][T14664] Code: 48 c1 ea 03 80 3c 02 00 0f 85 c1 04 00 00 49 8b 3c 24 e8 e4 b5 78 ff 84 c0 75 2d 4c 89 ee 48
> > > > > > [  298.776782][T14664] RSP: 0018:ffff88805b7df9b8 EFLAGS: 00010282[  298.777583][T14664] RAX: dffffc0000000008 RBX: ffff8880511725c0 RCX: 0000000000000000
> > > > > > [  298.778610][T14664] RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8880540c5c14
> > > > > > [  298.779637][T14664] RBP: 0000000000000000 R08: fffffbfff15235ad R09: 0000000000000000
> > > > > > [  298.780664][T14664] R10: 0000000000000001 R11: 0000000000000000 R12: ffffffffc06b5000
> > > > > > [  298.781702][T14664] R13: ffff88804c234a88 R14: ffff88804c22dd00 R15: ffffffff8a1b5660
> > > > > > [  298.782722][T14664] FS:  00007fafa13a8540(0000) GS:ffff88806c800000(0000) knlGS:0000000000000000
> > > > > > [  298.783845][T14664] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > > > [  298.784672][T14664] CR2: 00007fafa0e9cd10 CR3: 000000004b286005 CR4: 00000000000606e0
> > > > > > [  298.785739][T14664] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > > > > [  298.786769][T14664] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > > > > [  298.787785][T14664] Call Trace:
> > > > > > [  298.788237][T14664]  do_dentry_open+0x63c/0xf50
> > > > > > [  298.788872][T14664]  ? open_proxy_open+0x270/0x270
> > > > > > [  298.789524][T14664]  ? __x64_sys_fchdir+0x180/0x180
> > > > > > [  298.790169][T14664]  ? inode_permission+0x65/0x390
> > > > > > [  298.790832][T14664]  path_openat+0xc45/0x2680
> > > > > > [  298.791425][T14664]  ? save_stack+0x69/0x80
> > > > > > [  298.791988][T14664]  ? save_stack+0x19/0x80
> > > > > > [  298.792544][T14664]  ? path_mountpoint+0x2e0/0x2e0
> > > > > > [  298.793233][T14664]  ? check_chain_key+0x236/0x5d0
> > > > > > [  298.793910][T14664]  ? sched_clock_cpu+0x18/0x170
> > > > > > [  298.794527][T14664]  ? find_held_lock+0x39/0x1d0
> > > > > > [  298.795153][T14664]  do_filp_open+0x16a/0x260
> > > > > > [ ... ]
> > > > > >
> > > > > > Fixes: 9fd4dcece43a ("debugfs: prevent access to possibly dead file_operations at file open")
> > > > > > Reported-by: kbuild test robot <lkp@intel.com>
> > > > > > Signed-off-by: Taehee Yoo <ap420073@gmail.com>
> > > > > > ---
> > > > > >
> > > > > > v1 -> v2:
> > > > > >  - Fix compile error
> > > > > >
> > > > > >  fs/debugfs/file.c | 18 ++++++++++++++----
> > > > > >  1 file changed, 14 insertions(+), 4 deletions(-)
> > > > > >
> > > > > > diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> > > > > > index 634b09d18b77..e3075389fba0 100644
> > > > > > --- a/fs/debugfs/file.c
> > > > > > +++ b/fs/debugfs/file.c
> > > > > > @@ -175,8 +175,13 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
> > > > > >       if (r)
> > > > > >               goto out;
> > > > > >
> > > > > > -     real_fops = fops_get(real_fops);
> > > > > > -     if (!real_fops) {
> > > > > > +     if (!fops_get(real_fops)) {
> > > > > > +#ifdef MODULE
> > > > > > +             if (real_fops->owner &&
> > > > > > +                 real_fops->owner->state == MODULE_STATE_GOING)
> > > > > > +                     goto out;
> > > > > > +#endif
> > > > >
> > > > > Why is this in a #ifdef?
> > > > >
> > > > > The real_fops->owner field will be present if MODULE is not enabled,
> > > > > right?  Shouldn't this just work the same for that case?
> > > > >
> > > >
> > > > The reason for the #ifdef is to avoid compile error
> > > > MODULE_STATE_GOING is defined if CONFIG_MODULES is enabled.
> > >
> > > We should fix that in the .h file where that is defined so that we don't
> > > have to mess with stuff like this in a .c file.
> > >
> > > > So, If the #ifdef doesn't exist, compile will errors.
> > > > But honestly, I'm not sure whether CONFIG_MODULES should be used
> > > > here instead of MODULE or not.
> > >
> > > Neither, #ifdefs shouldn't be in .c files :)
> > >
> >
> > Thank you for the review.
> > I would like to move MODULE_STATE_XXX flags to outside of CONFIG_MODULES.
>
> That would be good.
>
> > In addition, I think a new inline function, which checks modules state
> > would be helpful for this case.
> > The inline function code would like this.
> >
> > +static inline bool module_is_going(struct module *mod)
> > +{
> > +       return mod->state == MODULE_STATE_GOING;
> > +}
>
> That too would be good, as there are a number of places in the kernel
> that could be cleaned up to use this.  Same for MODULE_STATE_COMING,
> right?
>

Thank you for the suggestion, I will make functions for all module
state flags.

> So a patch series with all of this would be appreciated.
>

I will send a new patchset.
Thank you so much for your review!
Taehee Yoo

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH v2] debugfs: Check module state before warning in {full/open}_proxy_open()
  2020-02-12  9:45           ` Taehee Yoo
@ 2020-02-12 15:39             ` Taehee Yoo
  0 siblings, 0 replies; 8+ messages in thread
From: Taehee Yoo @ 2020-02-12 15:39 UTC (permalink / raw)
  To: Greg KH; +Cc: rafael, linux-fsdevel

On Wed, 12 Feb 2020 at 18:45, Taehee Yoo <ap420073@gmail.com> wrote:
>
> On Wed, 12 Feb 2020 at 03:34, Greg KH <gregkh@linuxfoundation.org> wrote:
> >
>
> Hi Greg!
>
> > On Wed, Feb 12, 2020 at 02:18:38AM +0900, Taehee Yoo wrote:
> > > On Tue, 11 Feb 2020 at 21:28, Greg KH <gregkh@linuxfoundation.org> wrote:
> > > >
> > >
> > > Hi Greg!
> > >
> > > > On Tue, Feb 11, 2020 at 03:09:13PM +0900, Taehee Yoo wrote:
> > > > > On Tue, 11 Feb 2020 at 06:40, Greg KH <gregkh@linuxfoundation.org> wrote:
> > > > > >
> > > > >
> > > > > Hi Greg,
> > > > > Thank you for your review!
> > > > >
> > > > > > On Thu, Feb 06, 2020 at 06:47:56AM +0000, Taehee Yoo wrote:
> > > > > > > When the module is being removed, the module state is set to
> > > > > > > MODULE_STATE_GOING. At this point, try_module_get() fails.
> > > > > > > And when {full/open}_proxy_open() is being called,
> > > > > > > it calls try_module_get() to try to hold module reference count.
> > > > > > > If it fails, it warns about the possibility of debugfs file leak.
> > > > > > >
> > > > > > > If {full/open}_proxy_open() is called while the module is being removed,
> > > > > > > it fails to hold the module.
> > > > > > > So, It warns about debugfs file leak. But it is not the debugfs file
> > > > > > > leak case. So, this patch just adds module state checking routine
> > > > > > > in the {full/open}_proxy_open().
> > > > > > >
> > > > > > > Test commands:
> > > > > > >     #SHELL1
> > > > > > >     while :
> > > > > > >     do
> > > > > > >         modprobe netdevsim
> > > > > > >         echo 1 > /sys/bus/netdevsim/new_device
> > > > > > >         modprobe -rv netdevsim
> > > > > > >     done
> > > > > > >
> > > > > > >     #SHELL2
> > > > > > >     while :
> > > > > > >     do
> > > > > > >         cat /sys/kernel/debug/netdevsim/netdevsim1/ports/0/ipsec
> > > > > > >     done
> > > > > > >
> > > > > > > Splat looks like:
> > > > > > > [  298.766738][T14664] debugfs file owner did not clean up at exit: ipsec
> > > > > > > [  298.766766][T14664] WARNING: CPU: 2 PID: 14664 at fs/debugfs/file.c:312 full_proxy_open+0x10f/0x650
> > > > > > > [  298.768595][T14664] Modules linked in: netdevsim(-) openvswitch nsh nf_conncount nf_nat nf_conntrack nf_defrag_ipv6 n][  298.771343][T14664] CPU: 2 PID: 14664 Comm: cat Tainted: G        W         5.5.0+ #1
> > > > > > > [  298.772373][T14664] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
> > > > > > > [  298.773545][T14664] RIP: 0010:full_proxy_open+0x10f/0x650
> > > > > > > [  298.774247][T14664] Code: 48 c1 ea 03 80 3c 02 00 0f 85 c1 04 00 00 49 8b 3c 24 e8 e4 b5 78 ff 84 c0 75 2d 4c 89 ee 48
> > > > > > > [  298.776782][T14664] RSP: 0018:ffff88805b7df9b8 EFLAGS: 00010282[  298.777583][T14664] RAX: dffffc0000000008 RBX: ffff8880511725c0 RCX: 0000000000000000
> > > > > > > [  298.778610][T14664] RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff8880540c5c14
> > > > > > > [  298.779637][T14664] RBP: 0000000000000000 R08: fffffbfff15235ad R09: 0000000000000000
> > > > > > > [  298.780664][T14664] R10: 0000000000000001 R11: 0000000000000000 R12: ffffffffc06b5000
> > > > > > > [  298.781702][T14664] R13: ffff88804c234a88 R14: ffff88804c22dd00 R15: ffffffff8a1b5660
> > > > > > > [  298.782722][T14664] FS:  00007fafa13a8540(0000) GS:ffff88806c800000(0000) knlGS:0000000000000000
> > > > > > > [  298.783845][T14664] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > > > > [  298.784672][T14664] CR2: 00007fafa0e9cd10 CR3: 000000004b286005 CR4: 00000000000606e0
> > > > > > > [  298.785739][T14664] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > > > > > [  298.786769][T14664] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > > > > > [  298.787785][T14664] Call Trace:
> > > > > > > [  298.788237][T14664]  do_dentry_open+0x63c/0xf50
> > > > > > > [  298.788872][T14664]  ? open_proxy_open+0x270/0x270
> > > > > > > [  298.789524][T14664]  ? __x64_sys_fchdir+0x180/0x180
> > > > > > > [  298.790169][T14664]  ? inode_permission+0x65/0x390
> > > > > > > [  298.790832][T14664]  path_openat+0xc45/0x2680
> > > > > > > [  298.791425][T14664]  ? save_stack+0x69/0x80
> > > > > > > [  298.791988][T14664]  ? save_stack+0x19/0x80
> > > > > > > [  298.792544][T14664]  ? path_mountpoint+0x2e0/0x2e0
> > > > > > > [  298.793233][T14664]  ? check_chain_key+0x236/0x5d0
> > > > > > > [  298.793910][T14664]  ? sched_clock_cpu+0x18/0x170
> > > > > > > [  298.794527][T14664]  ? find_held_lock+0x39/0x1d0
> > > > > > > [  298.795153][T14664]  do_filp_open+0x16a/0x260
> > > > > > > [ ... ]
> > > > > > >
> > > > > > > Fixes: 9fd4dcece43a ("debugfs: prevent access to possibly dead file_operations at file open")
> > > > > > > Reported-by: kbuild test robot <lkp@intel.com>
> > > > > > > Signed-off-by: Taehee Yoo <ap420073@gmail.com>
> > > > > > > ---
> > > > > > >
> > > > > > > v1 -> v2:
> > > > > > >  - Fix compile error
> > > > > > >
> > > > > > >  fs/debugfs/file.c | 18 ++++++++++++++----
> > > > > > >  1 file changed, 14 insertions(+), 4 deletions(-)
> > > > > > >
> > > > > > > diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> > > > > > > index 634b09d18b77..e3075389fba0 100644
> > > > > > > --- a/fs/debugfs/file.c
> > > > > > > +++ b/fs/debugfs/file.c
> > > > > > > @@ -175,8 +175,13 @@ static int open_proxy_open(struct inode *inode, struct file *filp)
> > > > > > >       if (r)
> > > > > > >               goto out;
> > > > > > >
> > > > > > > -     real_fops = fops_get(real_fops);
> > > > > > > -     if (!real_fops) {
> > > > > > > +     if (!fops_get(real_fops)) {
> > > > > > > +#ifdef MODULE
> > > > > > > +             if (real_fops->owner &&
> > > > > > > +                 real_fops->owner->state == MODULE_STATE_GOING)
> > > > > > > +                     goto out;
> > > > > > > +#endif
> > > > > >
> > > > > > Why is this in a #ifdef?
> > > > > >
> > > > > > The real_fops->owner field will be present if MODULE is not enabled,
> > > > > > right?  Shouldn't this just work the same for that case?
> > > > > >
> > > > >
> > > > > The reason for the #ifdef is to avoid compile error
> > > > > MODULE_STATE_GOING is defined if CONFIG_MODULES is enabled.
> > > >
> > > > We should fix that in the .h file where that is defined so that we don't
> > > > have to mess with stuff like this in a .c file.
> > > >
> > > > > So, If the #ifdef doesn't exist, compile will errors.
> > > > > But honestly, I'm not sure whether CONFIG_MODULES should be used
> > > > > here instead of MODULE or not.
> > > >
> > > > Neither, #ifdefs shouldn't be in .c files :)
> > > >
> > >
> > > Thank you for the review.
> > > I would like to move MODULE_STATE_XXX flags to outside of CONFIG_MODULES.
> >
> > That would be good.
> >
> > > In addition, I think a new inline function, which checks modules state
> > > would be helpful for this case.
> > > The inline function code would like this.
> > >
> > > +static inline bool module_is_going(struct module *mod)
> > > +{
> > > +       return mod->state == MODULE_STATE_GOING;
> > > +}
> >
> > That too would be good, as there are a number of places in the kernel
> > that could be cleaned up to use this.  Same for MODULE_STATE_COMING,
> > right?
> >
>
> Thank you for the suggestion, I will make functions for all module
> state flags.
>
> > So a patch series with all of this would be appreciated.
> >
>
> I will send a new patchset.
> Thank you so much for your review!
> Taehee Yoo

Hi again,

I have tried to make this patch, but I found a problem.
I thought "struct module" and member variables can be used even
CONFIG_MODULES is disabled.
But It isn't.

/include/linux/module.h

42 struct module;
...
293 #ifdef CONFIG_MODULES
...
360 struct module {
...
523 } ____cacheline_aligned __randomize_layout;
...
700 #else /* !CONFIG_MODULES... */
...
847 #endif /* CONFIG_MODULES */


/include/linux/export.h

#ifdef MODULE
extern struct module __this_module;
#define THIS_MODULE (&__this_module)
#else
#define THIS_MODULE ((struct module *)0)
#endif

Checking module flags is impossible if CONFIG_MODULES is disabled.
So, I think the existence of the ifdef in .c file is not bad for this case.

Thank you
Taehee Yoo

^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, back to index

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-02-06  6:47 [PATCH v2] debugfs: Check module state before warning in {full/open}_proxy_open() Taehee Yoo
2020-02-10 21:40 ` Greg KH
2020-02-11  6:09   ` Taehee Yoo
2020-02-11 12:28     ` Greg KH
2020-02-11 17:18       ` Taehee Yoo
2020-02-11 18:34         ` Greg KH
2020-02-12  9:45           ` Taehee Yoo
2020-02-12 15:39             ` Taehee Yoo

Linux-Fsdevel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-fsdevel/0 linux-fsdevel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-fsdevel linux-fsdevel/ https://lore.kernel.org/linux-fsdevel \
		linux-fsdevel@vger.kernel.org
	public-inbox-index linux-fsdevel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-fsdevel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git