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* [PATCH] tty/vt: fix a memory leak in con_insert_unipair
@ 2020-08-09 22:14 James Bond
  2020-08-10  5:16 ` Jiri Slaby
  0 siblings, 1 reply; 4+ messages in thread
From: James Bond @ 2020-08-09 22:14 UTC (permalink / raw)
  To: jameslouisebond
  Cc: Greg Kroah-Hartman, Jiri Slaby, Andrew Morton, Kees Cook,
	Michel Lespinasse, Vlastimil Babka, Denis Efremov, linux-kernel

Syzkaller find a memory leak in con_insert_unipair:
    BUG: memory leak
    unreferenced object 0xffff88804893d100 (size 256):
    comm "syz-executor.3", pid 16154, jiffies 4295043307 (age 2392.340s)
    hex dump (first 32 bytes):
    80 af 88 4e 80 88 ff ff 00 a8 88 4e 80 88 ff ff  ...N.......N....
    80 ad 88 4e 80 88 ff ff 00 aa 88 4e 80 88 ff ff  ...N.......N....
    backtrace:
    [<00000000f76ff1de>] kmalloc include/linux/slab.h:555 [inline]
    [<00000000f76ff1de>] kmalloc_array include/linux/slab.h:596 [inline]
    [<00000000f76ff1de>] con_insert_unipair+0x9e/0x1a0 drivers/tty/vt/consolemap.c:482
    [<000000002f1ad7da>] con_set_unimap+0x244/0x2a0 drivers/tty/vt/consolemap.c:595
    [<0000000046ccb106>] do_unimap_ioctl drivers/tty/vt/vt_ioctl.c:297 [inline]
    [<0000000046ccb106>] vt_ioctl+0x863/0x12f0 drivers/tty/vt/vt_ioctl.c:1018
    [<00000000db1577ff>] tty_ioctl+0x4cd/0xa30 drivers/tty/tty_io.c:2656
    [<00000000e5cdf5ed>] vfs_ioctl fs/ioctl.c:48 [inline]
    [<00000000e5cdf5ed>] ksys_ioctl+0xa6/0xd0 fs/ioctl.c:753
    [<00000000fb4aa12c>] __do_sys_ioctl fs/ioctl.c:762 [inline]
    [<00000000fb4aa12c>] __se_sys_ioctl fs/ioctl.c:760 [inline]
    [<00000000fb4aa12c>] __x64_sys_ioctl+0x1a/0x20 fs/ioctl.c:760
    [<00000000f561f260>] do_syscall_64+0x4c/0xe0 arch/x86/entry/common.c:384
    [<0000000056206928>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
    BUG: leak checking failed

To fix this issue, we need to release the pointer p1 when the call of
the function kmalloc_array fail.

Signed-off-by: James Bond <jameslouisebond@gmail.com>
---
 drivers/tty/vt/consolemap.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
index 5947b54d92be..1e8d06c32ca1 100644
--- a/drivers/tty/vt/consolemap.c
+++ b/drivers/tty/vt/consolemap.c
@@ -489,7 +489,10 @@ con_insert_unipair(struct uni_pagedir *p, u_short unicode, u_short fontpos)
 	p2 = p1[n = (unicode >> 6) & 0x1f];
 	if (!p2) {
 		p2 = p1[n] = kmalloc_array(64, sizeof(u16), GFP_KERNEL);
-		if (!p2) return -ENOMEM;
+		if (!p2) {
+			kfree(p1);
+			return -ENOMEM;
+		}
 		memset(p2, 0xff, 64*sizeof(u16)); /* No glyphs for the characters (yet) */
 	}
 
-- 
2.17.1


^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] tty/vt: fix a memory leak in con_insert_unipair
  2020-08-09 22:14 [PATCH] tty/vt: fix a memory leak in con_insert_unipair James Bond
@ 2020-08-10  5:16 ` Jiri Slaby
  2020-08-10  7:51   ` Greg Kroah-Hartman
  0 siblings, 1 reply; 4+ messages in thread
From: Jiri Slaby @ 2020-08-10  5:16 UTC (permalink / raw)
  To: James Bond
  Cc: Greg Kroah-Hartman, Andrew Morton, Kees Cook, Michel Lespinasse,
	Vlastimil Babka, Denis Efremov, linux-kernel, Ben Hutchings

On 10. 08. 20, 0:14, James Bond wrote:
> Syzkaller find a memory leak in con_insert_unipair:
>     BUG: memory leak
>     unreferenced object 0xffff88804893d100 (size 256):
>     comm "syz-executor.3", pid 16154, jiffies 4295043307 (age 2392.340s)
>     hex dump (first 32 bytes):
>     80 af 88 4e 80 88 ff ff 00 a8 88 4e 80 88 ff ff  ...N.......N....
>     80 ad 88 4e 80 88 ff ff 00 aa 88 4e 80 88 ff ff  ...N.......N....
>     backtrace:
>     [<00000000f76ff1de>] kmalloc include/linux/slab.h:555 [inline]
>     [<00000000f76ff1de>] kmalloc_array include/linux/slab.h:596 [inline]
>     [<00000000f76ff1de>] con_insert_unipair+0x9e/0x1a0 drivers/tty/vt/consolemap.c:482
>     [<000000002f1ad7da>] con_set_unimap+0x244/0x2a0 drivers/tty/vt/consolemap.c:595
>     [<0000000046ccb106>] do_unimap_ioctl drivers/tty/vt/vt_ioctl.c:297 [inline]
>     [<0000000046ccb106>] vt_ioctl+0x863/0x12f0 drivers/tty/vt/vt_ioctl.c:1018
>     [<00000000db1577ff>] tty_ioctl+0x4cd/0xa30 drivers/tty/tty_io.c:2656
>     [<00000000e5cdf5ed>] vfs_ioctl fs/ioctl.c:48 [inline]
>     [<00000000e5cdf5ed>] ksys_ioctl+0xa6/0xd0 fs/ioctl.c:753
>     [<00000000fb4aa12c>] __do_sys_ioctl fs/ioctl.c:762 [inline]
>     [<00000000fb4aa12c>] __se_sys_ioctl fs/ioctl.c:760 [inline]
>     [<00000000fb4aa12c>] __x64_sys_ioctl+0x1a/0x20 fs/ioctl.c:760
>     [<00000000f561f260>] do_syscall_64+0x4c/0xe0 arch/x86/entry/common.c:384
>     [<0000000056206928>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>     BUG: leak checking failed
> 
> To fix this issue, we need to release the pointer p1 when the call of
> the function kmalloc_array fail.

This reminds me of:
commit 15b3cd8ef46ad1b100e0d3c7e38774f330726820
Author: Ben Hutchings <ben@decadent.org.uk>
Date:   Tue Jun 4 19:00:39 2019 +0100

    Revert "consolemap: Fix a memory leaking bug in
drivers/tty/vt/consolemap.c"

    This reverts commit 84ecc2f6eb1cb12e6d44818f94fa49b50f06e6ac.



So NACK.


Do we have some annotations for this instead?

> Signed-off-by: James Bond <jameslouisebond@gmail.com>
> ---
>  drivers/tty/vt/consolemap.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
> index 5947b54d92be..1e8d06c32ca1 100644
> --- a/drivers/tty/vt/consolemap.c
> +++ b/drivers/tty/vt/consolemap.c
> @@ -489,7 +489,10 @@ con_insert_unipair(struct uni_pagedir *p, u_short unicode, u_short fontpos)
>  	p2 = p1[n = (unicode >> 6) & 0x1f];
>  	if (!p2) {
>  		p2 = p1[n] = kmalloc_array(64, sizeof(u16), GFP_KERNEL);
> -		if (!p2) return -ENOMEM;
> +		if (!p2) {
> +			kfree(p1);
> +			return -ENOMEM;
> +		}
>  		memset(p2, 0xff, 64*sizeof(u16)); /* No glyphs for the characters (yet) */
>  	}

thanks,
-- 
js
suse labs

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] tty/vt: fix a memory leak in con_insert_unipair
  2020-08-10  5:16 ` Jiri Slaby
@ 2020-08-10  7:51   ` Greg Kroah-Hartman
  2020-08-10  8:14     ` Jiri Slaby
  0 siblings, 1 reply; 4+ messages in thread
From: Greg Kroah-Hartman @ 2020-08-10  7:51 UTC (permalink / raw)
  To: Jiri Slaby, James Bond
  Cc: Andrew Morton, Kees Cook, Michel Lespinasse, Vlastimil Babka,
	Denis Efremov, linux-kernel, Ben Hutchings

On Mon, Aug 10, 2020 at 07:16:48AM +0200, Jiri Slaby wrote:
> On 10. 08. 20, 0:14, James Bond wrote:
> > Syzkaller find a memory leak in con_insert_unipair:
> >     BUG: memory leak
> >     unreferenced object 0xffff88804893d100 (size 256):
> >     comm "syz-executor.3", pid 16154, jiffies 4295043307 (age 2392.340s)
> >     hex dump (first 32 bytes):
> >     80 af 88 4e 80 88 ff ff 00 a8 88 4e 80 88 ff ff  ...N.......N....
> >     80 ad 88 4e 80 88 ff ff 00 aa 88 4e 80 88 ff ff  ...N.......N....
> >     backtrace:
> >     [<00000000f76ff1de>] kmalloc include/linux/slab.h:555 [inline]
> >     [<00000000f76ff1de>] kmalloc_array include/linux/slab.h:596 [inline]
> >     [<00000000f76ff1de>] con_insert_unipair+0x9e/0x1a0 drivers/tty/vt/consolemap.c:482
> >     [<000000002f1ad7da>] con_set_unimap+0x244/0x2a0 drivers/tty/vt/consolemap.c:595
> >     [<0000000046ccb106>] do_unimap_ioctl drivers/tty/vt/vt_ioctl.c:297 [inline]
> >     [<0000000046ccb106>] vt_ioctl+0x863/0x12f0 drivers/tty/vt/vt_ioctl.c:1018
> >     [<00000000db1577ff>] tty_ioctl+0x4cd/0xa30 drivers/tty/tty_io.c:2656
> >     [<00000000e5cdf5ed>] vfs_ioctl fs/ioctl.c:48 [inline]
> >     [<00000000e5cdf5ed>] ksys_ioctl+0xa6/0xd0 fs/ioctl.c:753
> >     [<00000000fb4aa12c>] __do_sys_ioctl fs/ioctl.c:762 [inline]
> >     [<00000000fb4aa12c>] __se_sys_ioctl fs/ioctl.c:760 [inline]
> >     [<00000000fb4aa12c>] __x64_sys_ioctl+0x1a/0x20 fs/ioctl.c:760
> >     [<00000000f561f260>] do_syscall_64+0x4c/0xe0 arch/x86/entry/common.c:384
> >     [<0000000056206928>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >     BUG: leak checking failed
> > 
> > To fix this issue, we need to release the pointer p1 when the call of
> > the function kmalloc_array fail.
> 
> This reminds me of:
> commit 15b3cd8ef46ad1b100e0d3c7e38774f330726820
> Author: Ben Hutchings <ben@decadent.org.uk>
> Date:   Tue Jun 4 19:00:39 2019 +0100
> 
>     Revert "consolemap: Fix a memory leaking bug in
> drivers/tty/vt/consolemap.c"
> 
>     This reverts commit 84ecc2f6eb1cb12e6d44818f94fa49b50f06e6ac.
> 
> 
> 
> So NACK.

I have a whole talk just about the "fun" involved with that change:
	https://kernel-recipes.org/en/2019/talks/cves-are-dead-long-live-the-cve/

> Do we have some annotations for this instead?

We need something there, a comment saying "this is fine, don't touch
it!" or something like that?  We need that in a few other places in the
vt code as well.

> > Signed-off-by: James Bond <jameslouisebond@gmail.com>

Nice name...

James, can you mark this syzbot report as "invalid" or something like
that please so that this does not come up again and again.

thanks,

greg k-h

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] tty/vt: fix a memory leak in con_insert_unipair
  2020-08-10  7:51   ` Greg Kroah-Hartman
@ 2020-08-10  8:14     ` Jiri Slaby
  0 siblings, 0 replies; 4+ messages in thread
From: Jiri Slaby @ 2020-08-10  8:14 UTC (permalink / raw)
  To: Greg Kroah-Hartman, James Bond
  Cc: Andrew Morton, Kees Cook, Michel Lespinasse, Vlastimil Babka,
	Denis Efremov, linux-kernel, Ben Hutchings

On 10. 08. 20, 9:51, Greg Kroah-Hartman wrote:
> On Mon, Aug 10, 2020 at 07:16:48AM +0200, Jiri Slaby wrote:
>> On 10. 08. 20, 0:14, James Bond wrote:
>>> Syzkaller find a memory leak in con_insert_unipair:
>>>     BUG: memory leak
>>>     unreferenced object 0xffff88804893d100 (size 256):
>>>     comm "syz-executor.3", pid 16154, jiffies 4295043307 (age 2392.340s)
>>>     hex dump (first 32 bytes):
>>>     80 af 88 4e 80 88 ff ff 00 a8 88 4e 80 88 ff ff  ...N.......N....
>>>     80 ad 88 4e 80 88 ff ff 00 aa 88 4e 80 88 ff ff  ...N.......N....
>>>     backtrace:
>>>     [<00000000f76ff1de>] kmalloc include/linux/slab.h:555 [inline]
>>>     [<00000000f76ff1de>] kmalloc_array include/linux/slab.h:596 [inline]
>>>     [<00000000f76ff1de>] con_insert_unipair+0x9e/0x1a0 drivers/tty/vt/consolemap.c:482
>>>     [<000000002f1ad7da>] con_set_unimap+0x244/0x2a0 drivers/tty/vt/consolemap.c:595
>>>     [<0000000046ccb106>] do_unimap_ioctl drivers/tty/vt/vt_ioctl.c:297 [inline]
>>>     [<0000000046ccb106>] vt_ioctl+0x863/0x12f0 drivers/tty/vt/vt_ioctl.c:1018
>>>     [<00000000db1577ff>] tty_ioctl+0x4cd/0xa30 drivers/tty/tty_io.c:2656
>>>     [<00000000e5cdf5ed>] vfs_ioctl fs/ioctl.c:48 [inline]
>>>     [<00000000e5cdf5ed>] ksys_ioctl+0xa6/0xd0 fs/ioctl.c:753
>>>     [<00000000fb4aa12c>] __do_sys_ioctl fs/ioctl.c:762 [inline]
>>>     [<00000000fb4aa12c>] __se_sys_ioctl fs/ioctl.c:760 [inline]
>>>     [<00000000fb4aa12c>] __x64_sys_ioctl+0x1a/0x20 fs/ioctl.c:760
>>>     [<00000000f561f260>] do_syscall_64+0x4c/0xe0 arch/x86/entry/common.c:384
>>>     [<0000000056206928>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>>     BUG: leak checking failed
>>>
>>> To fix this issue, we need to release the pointer p1 when the call of
>>> the function kmalloc_array fail.
...
>> Do we have some annotations for this instead?
> 
> We need something there, a comment saying "this is fine, don't touch
> it!" or something like that?  We need that in a few other places in the
> vt code as well.

Sure, comment as the last resort (to silence patch writers). But I had
some kmemleak annotation (to silence the warning) in mind.

Or better fix/tune kmemleak: why it dares to think it's a mem leak in
the first place?

thanks,
-- 
js

^ permalink raw reply	[flat|nested] 4+ messages in thread

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Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2020-08-09 22:14 [PATCH] tty/vt: fix a memory leak in con_insert_unipair James Bond
2020-08-10  5:16 ` Jiri Slaby
2020-08-10  7:51   ` Greg Kroah-Hartman
2020-08-10  8:14     ` Jiri Slaby

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