From: Casey Schaufler <casey@schaufler-ca.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: CHANDAN VN <chandan.vn@samsung.com>,
gregkh@linuxfoundation.org, tj@kernel.org, bfields@fieldses.org,
jlayton@kernel.org, linux-kernel@vger.kernel.org,
linux-nfs@vger.kernel.org, cpgs@samsung.com,
sireesha.t@samsung.com, Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [PATCH 1/1] Fix memory leak in kernfs_security_xattr_set and kernfs_security_xattr_set
Date: Thu, 31 May 2018 14:08:14 -0700 [thread overview]
Message-ID: <9fb8de9d-3a9a-706b-50a9-11e768f72851@schaufler-ca.com> (raw)
In-Reply-To: <87po1ba6hv.fsf@xmission.com>
On 5/31/2018 1:57 PM, Eric W. Biederman wrote:
> Casey Schaufler <casey@schaufler-ca.com> writes:
>
>> On 5/31/2018 2:28 AM, CHANDAN VN wrote:
>>> From: "sireesha.t" <sireesha.t@samsung.com>
>>>
>>> Leak is caused because smack_inode_getsecurity() is allocating memory
>>> using kstrdup(). Though the security_release_secctx() is called, it
>>> would not free the allocated memory. Calling security_release_secctx is
>>> not relevant for this scenario as inode_getsecurity() does not provide a
>>> "secctx".
>>>
>>> Similar fix has been mainlined:
>>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?id=57e7ba04d422c3d41c8426380303ec9b7533ded9
>>>
>>> The fix is to replace the security_release_secctx() with a kfree()
>>>
>>> Below is the KMEMLEAK dump:
>>> unreferenced object 0xffffffc025e11c80 (size 64):
>>> comm "systemd-tmpfile", pid 2452, jiffies 4294894464 (age 235587.492s)
>>> hex dump (first 32 bytes):
>>> 53 79 73 74 65 6d 3a 3a 53 68 61 72 65 64 00 00 System::Shared..
>>> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>>> backtrace:
>>> [<ffffff80081be770>] __save_stack_trace+0x28/0x34
>>> [<ffffff80081bedb8>] create_object+0x130/0x25c
>>> [<ffffff80088c82f8>] kmemleak_alloc+0x30/0x5c
>>> [<ffffff80081b3ef0>] __kmalloc_track_caller+0x1cc/0x2a8
>>> [<ffffff800818673c>] kstrdup+0x3c/0x6c
>>> [<ffffff80082d78b0>] smack_inode_getsecurity+0xcc/0xec
>>> [<ffffff80082d78f4>] smack_inode_getsecctx+0x24/0x44
>>> [<ffffff80082d5ea0>] security_inode_getsecctx+0x50/0x70
>>> [<ffffff800823bbcc>] kernfs_security_xattr_set+0x74/0xe0
>>> [<ffffff80081eafec>] __vfs_setxattr+0x74/0x90
>>> [<ffffff80081eb088>] __vfs_setxattr_noperm+0x80/0x1ac
>>> [<ffffff80081eb238>] vfs_setxattr+0x84/0xac
>>> [<ffffff80081eb374>] setxattr+0x114/0x178
>>> [<ffffff80081eb44c>] path_setxattr+0x74/0xb8
>>> [<ffffff80081ebdcc>] SyS_lsetxattr+0x10/0x1c
>>> [<ffffff800808310c>] __sys_trace_return+0x0/0x4
>>>
>>> Signed-off-by: sireesha.t <sireesha.t@samsung.com>
>>> Signed-off-by: CHANDAN VN <chandan.vn@samsung.com>
>> Why not:
>>
>> static int smack_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
>> {
>> - int len = 0;
>> - len = smack_inode_getsecurity(inode, XATTR_SMACK_SUFFIX, ctx, true);
>> + int len = smack_inode_getsecurity(inode, XATTR_SMACK_SUFFIX, ctx, false);
>>
> The practical difference here is the true vs the false in the call
> to smack_inode_getsecurity?
That is correct. The author of smack_inode_getsecctx() has a SELinux
background and appears to have missed that Smack is careful not to
allocate memory and make copies of labels when it doesn't need to.
>
>> if (len < 0)
>> return len;
>>
> Eric
>
next prev parent reply other threads:[~2018-05-31 21:08 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20180531092848epcas1p24b638ccd6da00f1e039bdb64de7e1a5b@epcas1p2.samsung.com>
2018-05-31 9:28 ` [PATCH 1/1] Fix memory leak in kernfs_security_xattr_set and kernfs_security_xattr_set CHANDAN VN
2018-05-31 15:26 ` Casey Schaufler
2018-05-31 20:57 ` Eric W. Biederman
2018-05-31 21:08 ` Casey Schaufler [this message]
2018-05-31 15:39 ` Tejun Heo
2018-05-31 16:04 ` Casey Schaufler
2018-05-31 16:11 ` Tejun Heo
2018-05-31 16:22 ` Casey Schaufler
[not found] ` <CGME20180531092848epcas1p24b638ccd6da00f1e039bdb64de7e1a5b@epcms5p5>
2018-06-01 8:56 ` CHANDAN VN
2018-06-01 16:22 ` Casey Schaufler
[not found] ` <CGME20180531092848epcas1p24b638ccd6da00f1e039bdb64de7e1a5b@epcms5p7>
2018-06-01 16:29 ` CHANDAN VN
2018-06-01 16:41 ` Casey Schaufler
2018-06-01 17:45 ` [PATCH] Smack: Fix memory leak in smack_inode_getsecctx Casey Schaufler
2018-06-04 21:01 ` Casey Schaufler
2018-06-04 21:27 ` Tejun Heo
[not found] ` <CGME20180531092848epcas1p24b638ccd6da00f1e039bdb64de7e1a5b@epcms5p3>
2018-06-05 7:04 ` CHANDAN VN
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