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* [PATCH v2] relay: handle alloc_percpu returning NULL in relay_open
@ 2019-12-19 12:12 Daniel Axtens
  2019-12-20 19:00 ` David Rientjes
  0 siblings, 1 reply; 5+ messages in thread
From: Daniel Axtens @ 2019-12-19 12:12 UTC (permalink / raw)
  To: linux-kernel, viro
  Cc: ajd, mpe, Daniel Axtens, syzbot+1e925b4b836afe85a1c6,
	syzbot+587b2421926808309d21, syzbot+58320b7171734bf79d26,
	syzbot+d6074fb08bdb2e010520

alloc_percpu() may return NULL, which means chan->buf may be set to
NULL. In that case, when we do *per_cpu_ptr(chan->buf, ...), we
dereference an invalid pointer:

BUG: Unable to handle kernel data access at 0x7dae0000
Faulting instruction address: 0xc0000000003f3fec
...
NIP [c0000000003f3fec] relay_open+0x29c/0x600
LR [c0000000003f3fc0] relay_open+0x270/0x600
Call Trace:
[c000000054353a70] [c0000000003f3fb4] relay_open+0x264/0x600 (unreliable)
[c000000054353b00] [c000000000451764] __blk_trace_setup+0x254/0x600
[c000000054353bb0] [c000000000451b78] blk_trace_setup+0x68/0xa0
[c000000054353c10] [c0000000010da77c] sg_ioctl+0x7bc/0x2e80
[c000000054353cd0] [c000000000758cbc] do_vfs_ioctl+0x13c/0x1300
[c000000054353d90] [c000000000759f14] ksys_ioctl+0x94/0x130
[c000000054353de0] [c000000000759ff8] sys_ioctl+0x48/0xb0
[c000000054353e20] [c00000000000bcd0] system_call+0x5c/0x68

Check if alloc_percpu returns NULL.

This was found by syzkaller both on x86 and powerpc, and the reproducer
it found on powerpc is capable of hitting the issue as an unprivileged
user.

Fixes: 017c59c042d0 ("relay: Use per CPU constructs for the relay channel buffer pointers")
Reported-by: syzbot+1e925b4b836afe85a1c6@syzkaller-ppc64.appspotmail.com
Reported-by: syzbot+587b2421926808309d21@syzkaller-ppc64.appspotmail.com
Reported-by: syzbot+58320b7171734bf79d26@syzkaller.appspotmail.com
Reported-by: syzbot+d6074fb08bdb2e010520@syzkaller.appspotmail.com
Cc: Akash Goel <akash.goel@intel.com>
Cc: Andrew Donnellan <ajd@linux.ibm.com> # syzkaller-ppc64
Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Cc: stable@vger.kernel.org # v4.10+
Signed-off-by: Daniel Axtens <dja@axtens.net>

--

v2: drop the NOWARN.

There's a syz reproducer on the powerpc syzbot that eventually hits
the bug, but it can take up to an hour or so before it keels over on a
kernel with all the syzkaller debugging on, and even longer on a
production kernel. I have been able to reproduce it once on a stock
Ubuntu 5.0 ppc64le kernel.

CVE-2019-19462 has been assigned. While only the process doing the syscall
gets killed, it gets killed while holding the relay_channels_mutex,
so it blocks all future relay activity.
---
 kernel/relay.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/relay.c b/kernel/relay.c
index ade14fb7ce2e..4b760ec16342 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -581,6 +581,11 @@ struct rchan *relay_open(const char *base_filename,
 		return NULL;
 
 	chan->buf = alloc_percpu(struct rchan_buf *);
+	if (!chan->buf) {
+		kfree(chan);
+		return NULL;
+	}
+
 	chan->version = RELAYFS_CHANNEL_VERSION;
 	chan->n_subbufs = n_subbufs;
 	chan->subbuf_size = subbuf_size;
-- 
2.20.1


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH v2] relay: handle alloc_percpu returning NULL in relay_open
  2019-12-19 12:12 [PATCH v2] relay: handle alloc_percpu returning NULL in relay_open Daniel Axtens
@ 2019-12-20 19:00 ` David Rientjes
  2020-05-21 15:25   ` Salvatore Bonaccorso
  0 siblings, 1 reply; 5+ messages in thread
From: David Rientjes @ 2019-12-20 19:00 UTC (permalink / raw)
  To: Daniel Axtens
  Cc: linux-kernel, viro, ajd, mpe, syzbot+1e925b4b836afe85a1c6,
	syzbot+587b2421926808309d21, syzbot+58320b7171734bf79d26,
	syzbot+d6074fb08bdb2e010520

On Thu, 19 Dec 2019, Daniel Axtens wrote:

> alloc_percpu() may return NULL, which means chan->buf may be set to
> NULL. In that case, when we do *per_cpu_ptr(chan->buf, ...), we
> dereference an invalid pointer:
> 
> BUG: Unable to handle kernel data access at 0x7dae0000
> Faulting instruction address: 0xc0000000003f3fec
> ...
> NIP [c0000000003f3fec] relay_open+0x29c/0x600
> LR [c0000000003f3fc0] relay_open+0x270/0x600
> Call Trace:
> [c000000054353a70] [c0000000003f3fb4] relay_open+0x264/0x600 (unreliable)
> [c000000054353b00] [c000000000451764] __blk_trace_setup+0x254/0x600
> [c000000054353bb0] [c000000000451b78] blk_trace_setup+0x68/0xa0
> [c000000054353c10] [c0000000010da77c] sg_ioctl+0x7bc/0x2e80
> [c000000054353cd0] [c000000000758cbc] do_vfs_ioctl+0x13c/0x1300
> [c000000054353d90] [c000000000759f14] ksys_ioctl+0x94/0x130
> [c000000054353de0] [c000000000759ff8] sys_ioctl+0x48/0xb0
> [c000000054353e20] [c00000000000bcd0] system_call+0x5c/0x68
> 
> Check if alloc_percpu returns NULL.
> 
> This was found by syzkaller both on x86 and powerpc, and the reproducer
> it found on powerpc is capable of hitting the issue as an unprivileged
> user.
> 
> Fixes: 017c59c042d0 ("relay: Use per CPU constructs for the relay channel buffer pointers")
> Reported-by: syzbot+1e925b4b836afe85a1c6@syzkaller-ppc64.appspotmail.com
> Reported-by: syzbot+587b2421926808309d21@syzkaller-ppc64.appspotmail.com
> Reported-by: syzbot+58320b7171734bf79d26@syzkaller.appspotmail.com
> Reported-by: syzbot+d6074fb08bdb2e010520@syzkaller.appspotmail.com
> Cc: Akash Goel <akash.goel@intel.com>
> Cc: Andrew Donnellan <ajd@linux.ibm.com> # syzkaller-ppc64
> Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>
> Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
> Cc: stable@vger.kernel.org # v4.10+
> Signed-off-by: Daniel Axtens <dja@axtens.net>

Acked-by: David Rientjes <rientjes@google.com>

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH v2] relay: handle alloc_percpu returning NULL in relay_open
  2019-12-20 19:00 ` David Rientjes
@ 2020-05-21 15:25   ` Salvatore Bonaccorso
  2020-05-25  1:52     ` Daniel Axtens
  0 siblings, 1 reply; 5+ messages in thread
From: Salvatore Bonaccorso @ 2020-05-21 15:25 UTC (permalink / raw)
  To: David Rientjes
  Cc: Daniel Axtens, linux-kernel, viro, ajd, mpe,
	syzbot+1e925b4b836afe85a1c6, syzbot+587b2421926808309d21,
	syzbot+58320b7171734bf79d26, syzbot+d6074fb08bdb2e010520,
	Guenter Roeck

Hi,

On Fri, Dec 20, 2019 at 11:00:56AM -0800, David Rientjes wrote:
> On Thu, 19 Dec 2019, Daniel Axtens wrote:
> 
> > alloc_percpu() may return NULL, which means chan->buf may be set to
> > NULL. In that case, when we do *per_cpu_ptr(chan->buf, ...), we
> > dereference an invalid pointer:
> > 
> > BUG: Unable to handle kernel data access at 0x7dae0000
> > Faulting instruction address: 0xc0000000003f3fec
> > ...
> > NIP [c0000000003f3fec] relay_open+0x29c/0x600
> > LR [c0000000003f3fc0] relay_open+0x270/0x600
> > Call Trace:
> > [c000000054353a70] [c0000000003f3fb4] relay_open+0x264/0x600 (unreliable)
> > [c000000054353b00] [c000000000451764] __blk_trace_setup+0x254/0x600
> > [c000000054353bb0] [c000000000451b78] blk_trace_setup+0x68/0xa0
> > [c000000054353c10] [c0000000010da77c] sg_ioctl+0x7bc/0x2e80
> > [c000000054353cd0] [c000000000758cbc] do_vfs_ioctl+0x13c/0x1300
> > [c000000054353d90] [c000000000759f14] ksys_ioctl+0x94/0x130
> > [c000000054353de0] [c000000000759ff8] sys_ioctl+0x48/0xb0
> > [c000000054353e20] [c00000000000bcd0] system_call+0x5c/0x68
> > 
> > Check if alloc_percpu returns NULL.
> > 
> > This was found by syzkaller both on x86 and powerpc, and the reproducer
> > it found on powerpc is capable of hitting the issue as an unprivileged
> > user.
> > 
> > Fixes: 017c59c042d0 ("relay: Use per CPU constructs for the relay channel buffer pointers")
> > Reported-by: syzbot+1e925b4b836afe85a1c6@syzkaller-ppc64.appspotmail.com
> > Reported-by: syzbot+587b2421926808309d21@syzkaller-ppc64.appspotmail.com
> > Reported-by: syzbot+58320b7171734bf79d26@syzkaller.appspotmail.com
> > Reported-by: syzbot+d6074fb08bdb2e010520@syzkaller.appspotmail.com
> > Cc: Akash Goel <akash.goel@intel.com>
> > Cc: Andrew Donnellan <ajd@linux.ibm.com> # syzkaller-ppc64
> > Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>
> > Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
> > Cc: stable@vger.kernel.org # v4.10+
> > Signed-off-by: Daniel Axtens <dja@axtens.net>
> 
> Acked-by: David Rientjes <rientjes@google.com>

It looks this one was never applied (which relates to CVE-2019-19462,
as pointed by Guenter in 20191223163610.GA32267@roeck-us.net).

Whas this lost or are there any issues pending?

Regards,
Salvatore

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH v2] relay: handle alloc_percpu returning NULL in relay_open
  2020-05-21 15:25   ` Salvatore Bonaccorso
@ 2020-05-25  1:52     ` Daniel Axtens
  2020-05-26  3:25       ` Michael Ellerman
  0 siblings, 1 reply; 5+ messages in thread
From: Daniel Axtens @ 2020-05-25  1:52 UTC (permalink / raw)
  To: Salvatore Bonaccorso, David Rientjes
  Cc: linux-kernel, viro, ajd, mpe, syzbot+1e925b4b836afe85a1c6,
	syzbot+587b2421926808309d21, syzbot+58320b7171734bf79d26,
	syzbot+d6074fb08bdb2e010520, Guenter Roeck

>> > Check if alloc_percpu returns NULL.
>> > 
>> > This was found by syzkaller both on x86 and powerpc, and the reproducer
>> > it found on powerpc is capable of hitting the issue as an unprivileged
>> > user.
>> > 
>> > Fixes: 017c59c042d0 ("relay: Use per CPU constructs for the relay channel buffer pointers")
>> > Reported-by: syzbot+1e925b4b836afe85a1c6@syzkaller-ppc64.appspotmail.com
>> > Reported-by: syzbot+587b2421926808309d21@syzkaller-ppc64.appspotmail.com
>> > Reported-by: syzbot+58320b7171734bf79d26@syzkaller.appspotmail.com
>> > Reported-by: syzbot+d6074fb08bdb2e010520@syzkaller.appspotmail.com
>> > Cc: Akash Goel <akash.goel@intel.com>
>> > Cc: Andrew Donnellan <ajd@linux.ibm.com> # syzkaller-ppc64
>> > Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>
>> > Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
>> > Cc: stable@vger.kernel.org # v4.10+
>> > Signed-off-by: Daniel Axtens <dja@axtens.net>
>> 
>> Acked-by: David Rientjes <rientjes@google.com>
>
> It looks this one was never applied (which relates to CVE-2019-19462,
> as pointed by Guenter in 20191223163610.GA32267@roeck-us.net).
>
> Whas this lost or are there any issues pending?

I'm not aware of any pending issues.

(But, if anyone does have any objections I'm happy to revise the patch.)

Regards,
Daniel

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH v2] relay: handle alloc_percpu returning NULL in relay_open
  2020-05-25  1:52     ` Daniel Axtens
@ 2020-05-26  3:25       ` Michael Ellerman
  0 siblings, 0 replies; 5+ messages in thread
From: Michael Ellerman @ 2020-05-26  3:25 UTC (permalink / raw)
  To: Andrew Morton
  Cc: linux-kernel, viro, ajd, syzbot+1e925b4b836afe85a1c6,
	syzbot+587b2421926808309d21, syzbot+58320b7171734bf79d26,
	syzbot+d6074fb08bdb2e010520, Guenter Roeck, Daniel Axtens,
	Salvatore Bonaccorso, David Rientjes

[ + akpm ]

Daniel Axtens <dja@axtens.net> writes:
>>> > Check if alloc_percpu returns NULL.
>>> > 
>>> > This was found by syzkaller both on x86 and powerpc, and the reproducer
>>> > it found on powerpc is capable of hitting the issue as an unprivileged
>>> > user.
>>> > 
>>> > Fixes: 017c59c042d0 ("relay: Use per CPU constructs for the relay channel buffer pointers")
>>> > Reported-by: syzbot+1e925b4b836afe85a1c6@syzkaller-ppc64.appspotmail.com
>>> > Reported-by: syzbot+587b2421926808309d21@syzkaller-ppc64.appspotmail.com
>>> > Reported-by: syzbot+58320b7171734bf79d26@syzkaller.appspotmail.com
>>> > Reported-by: syzbot+d6074fb08bdb2e010520@syzkaller.appspotmail.com
>>> > Cc: Akash Goel <akash.goel@intel.com>
>>> > Cc: Andrew Donnellan <ajd@linux.ibm.com> # syzkaller-ppc64
>>> > Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>
>>> > Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
>>> > Cc: stable@vger.kernel.org # v4.10+
>>> > Signed-off-by: Daniel Axtens <dja@axtens.net>
>>> 
>>> Acked-by: David Rientjes <rientjes@google.com>
>>
>> It looks this one was never applied (which relates to CVE-2019-19462,
>> as pointed by Guenter in 20191223163610.GA32267@roeck-us.net).
>>
>> Whas this lost or are there any issues pending?
>
> I'm not aware of any pending issues.
>
> (But, if anyone does have any objections I'm happy to revise the patch.)

It looks like kernel/relay.c is lacking a maintainer?

Andrew are you able to pick this up for v5.8? It's pretty obviously
correct, and has David's ack.

Original is here if that helps:
  https://lore.kernel.org/lkml/20191219121256.26480-1-dja@axtens.net/


cheers

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2020-05-26  3:25 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-12-19 12:12 [PATCH v2] relay: handle alloc_percpu returning NULL in relay_open Daniel Axtens
2019-12-20 19:00 ` David Rientjes
2020-05-21 15:25   ` Salvatore Bonaccorso
2020-05-25  1:52     ` Daniel Axtens
2020-05-26  3:25       ` Michael Ellerman

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