linux-kernel - [PATCH] ucount: mark user_header with kmemleak

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Date:   Fri,  3 Feb 2017 13:14:04 -0800
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     ebiederm@...ssion.com, keescook@...omium.org,
        n.borisov.lkml@...il.com, akpm@...ux-foundation.org
Cc:     serge@...lyn.com, jack@...e.cz, linux-kernel@...r.kernel.org,
        "Luis R. Rodriguez" <mcgrof@...nel.org>
Subject: [PATCH] ucount: mark user_header with kmemleak_ignore()

The user_header gets caught by kmemleak with the following splat
as missing a free:

unreferenced object 0xffff99667a733d80 (size 96):
  comm "swapper/0", pid 1, jiffies 4294892317 (age 62191.468s)
  hex dump (first 32 bytes):
    a0 b6 92 b4 ff ff ff ff 00 00 00 00 01 00 00 00  ................
    01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffffb3a5f7ea>] kmemleak_alloc+0x4a/0xa0
    [<ffffffffb36050d4>] __kmalloc+0x144/0x260
    [<ffffffffb36a7144>] __register_sysctl_table+0x54/0x5e0
    [<ffffffffb36a76eb>] register_sysctl+0x1b/0x20
    [<ffffffffb416fe17>] user_namespace_sysctl_init+0x17/0x34
    [<ffffffffb3402192>] do_one_initcall+0x52/0x1a0
    [<ffffffffb414d1bd>] kernel_init_freeable+0x173/0x200
    [<ffffffffb3a5c23e>] kernel_init+0xe/0x100
    [<ffffffffb3a6b57c>] ret_from_fork+0x2c/0x40
    [<ffffffffffffffff>] 0xffffffffffffffff

The BUG_ON()s are intended to crash so no need to clean up after
ourselves on error there. This is also a kernel/ subsys_init() we
don't need a respective exit call here as this is never modular,
so just white list it.

Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
---
 kernel/ucount.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/ucount.c b/kernel/ucount.c
index 68716403b261..8a11fc0cb459 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -231,11 +231,10 @@ static __init int user_namespace_sysctl_init(void)
 	 * properly.
 	 */
 	user_header = register_sysctl("user", empty);
+	kmemleak_ignore(user_header);
 	BUG_ON(!user_header);
 	BUG_ON(!setup_userns_sysctls(&init_user_ns));
 #endif
 	return 0;
 }
 subsys_initcall(user_namespace_sysctl_init);
-
-
-- 
2.11.0