linux-kernel - [PATCH 1/1] Fix memory leak in kernfs_security_xattr_set and kernfs_security_xattr

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Message-id: <1527758911-18610-1-git-send-email-chandan.vn@samsung.com>
Date:   Thu, 31 May 2018 14:58:31 +0530
From:   CHANDAN VN <chandan.vn@...sung.com>
To:     gregkh@...uxfoundation.org, tj@...nel.org, bfields@...ldses.org,
        jlayton@...nel.org, linux-kernel@...r.kernel.org,
        linux-nfs@...r.kernel.org, casey@...aufler-ca.com
Cc:     cpgs@...sung.com, chandan.vn@...sung.com, sireesha.t@...sung.com
Subject: [PATCH 1/1] Fix memory leak in kernfs_security_xattr_set and
 kernfs_security_xattr_set

From: "sireesha.t" <sireesha.t@...sung.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@...sung.com>
Signed-off-by: CHANDAN VN <chandan.vn@...sung.com>
---
 fs/kernfs/inode.c | 3 ++-
 fs/nfsd/nfs4xdr.c | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index a343039..53befb8 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -369,7 +369,8 @@ static int kernfs_security_xattr_set(const struct xattr_handler *handler,
 	mutex_unlock(&kernfs_mutex);
 
 	if (secdata)
-		security_release_secctx(secdata, secdata_len);
+		kfree(secdata);
+
 	return error;
 }
 
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index aaa88c1..1e0dbe9 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2911,7 +2911,7 @@ static int get_parent_attributes(struct svc_export *exp, struct kstat *stat)
 out:
 #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
 	if (context)
-		security_release_secctx(context, contextlen);
+		kfree(context);
 #endif /* CONFIG_NFSD_V4_SECURITY_LABEL */
 	kfree(acl);
 	if (tempfh) {
-- 
1.9.1