ACK: [hardy, lucid, lucid/fsl-imx51, maverick, maverick/ti-omap4, natty, natty/ti-omap4 CVE 1/1] KEYS: Fix a NULL pointer deref in the user-defined key type

Tim Gardner tim.gardner at canonical.com
Tue Dec 6 16:49:02 UTC 2011


On 12/06/2011 09:32 AM, Andy Whitcroft wrote:
> From: David Howells<dhowells at redhat.com>
>
> Fix a NULL pointer deref in the user-defined key type whereby updating a
> negative key into a fully instantiated key will cause an oops to occur
> when the code attempts to free the non-existent old payload.
>
> This results in an oops that looks something like the following:
>
>    BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
>    IP: [<ffffffff81085fa1>] __call_rcu+0x11/0x13e
>    PGD 3391d067 PUD 3894a067 PMD 0
>    Oops: 0002 [#1] SMP
>    CPU 1
>    Pid: 4354, comm: keyctl Not tainted 3.1.0-fsdevel+ #1140                  /DG965RY
>    RIP: 0010:[<ffffffff81085fa1>]  [<ffffffff81085fa1>] __call_rcu+0x11/0x13e
>    RSP: 0018:ffff88003d591df8  EFLAGS: 00010246
>    RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000000000000006e
>    RDX: ffffffff8161d0c0 RSI: 0000000000000000 RDI: 0000000000000000
>    RBP: ffff88003d591e18 R08: 0000000000000000 R09: ffffffff8152fa6c
>    R10: 0000000000000000 R11: 0000000000000300 R12: ffff88003b8f9538
>    R13: ffffffff8161d0c0 R14: ffff88003b8f9d50 R15: ffff88003c69f908
>    FS:  00007f97eb18c720(0000) GS:ffff88003bd00000(0000) knlGS:0000000000000000
>    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>    CR2: 0000000000000008 CR3: 000000003d47a000 CR4: 00000000000006e0
>    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>    DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
>    Process keyctl (pid: 4354, threadinfo ffff88003d590000, task ffff88003c78a040)
>    Stack:
>     ffff88003e0ffde0 ffff88003b8f9538 0000000000000001 ffff88003b8f9d50
>     ffff88003d591e28 ffffffff810860f0 ffff88003d591e68 ffffffff8117bfea
>     ffff88003d591e68 ffffffff00000000 ffff88003e0ffde1 ffff88003e0ffde0
>    Call Trace:
>     [<ffffffff810860f0>] call_rcu_sched+0x10/0x12
>     [<ffffffff8117bfea>] user_update+0x8d/0xa2
>     [<ffffffff8117723a>] key_create_or_update+0x236/0x270
>     [<ffffffff811789b1>] sys_add_key+0x123/0x17e
>     [<ffffffff813b84bb>] system_call_fastpath+0x16/0x1b
>
> Signed-off-by: David Howells<dhowells at redhat.com>
> Acked-by: Jeff Layton<jlayton at redhat.com>
> Acked-by: Neil Horman<nhorman at redhat.com>
> Acked-by: Steve Dickson<steved at redhat.com>
> Acked-by: James Morris<jmorris at namei.org>
> Cc: stable at kernel.org
> Signed-off-by: Linus Torvalds<torvalds at linux-foundation.org>
>
> (backported from commit 9f35a33b8d06263a165efe3541d9aa0cdbd70b3b)
> CVE-2011-4110
> BugLink: http://bugs.launchpad.net/bugs/894369
> Signed-off-by: Andy Whitcroft<apw at canonical.com>
> ---
>   security/keys/user_defined.c |    3 ++-
>   1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c
> index 7c687d5..97edf29 100644
> --- a/security/keys/user_defined.c
> +++ b/security/keys/user_defined.c
> @@ -119,7 +119,8 @@ int user_update(struct key *key, const void *data, size_t datalen)
>   		key->expiry = 0;
>   	}
>
> -	call_rcu(&zap->rcu, user_update_rcu_disposal);
> +	if (zap)
> +		call_rcu(&zap->rcu, user_update_rcu_disposal);
>
>   error:
>   	return ret;


-- 
Tim Gardner tim.gardner at canonical.com




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