[PATCH 5.18 126/141] selinux: free contexts previously transferred in selinux_add_opt()

Greg Kroah-Hartman
2022-06-20T13:10:39Z

From: Christian Göttsche <cgzones@googlemail.com>

commit cad140d00899e7a9cb6fe93b282051df589e671c upstream.

`selinux_add_opt()` stopped taking ownership of the passed context since
commit 70f4169ab421 ("selinux: parse contexts for mount options early").

unreferenced object 0xffff888114dfd140 (size 64):
comm "mount", pid 15182, jiffies 4295687028 (age 796.340s)
hex dump (first 32 bytes):
73 79 73 74 65 6d 5f 75 3a 6f 62 6a 65 63 74 5f system_u:object_
72 3a 74 65 73 74 5f 66 69 6c 65 73 79 73 74 65 r:test_filesyste
backtrace:
[<ffffffffa07dbef4>] kmemdup_nul+0x24/0x80
[<ffffffffa0d34253>] selinux_sb_eat_lsm_opts+0x293/0x560
[<ffffffffa0d13f08>] security_sb_eat_lsm_opts+0x58/0x80
[<ffffffffa0af1eb2>] generic_parse_monolithic+0x82/0x180
[<ffffffffa0a9c1a5>] do_new_mount+0x1f5/0x550
[<ffffffffa0a9eccb>] path_mount+0x2ab/0x1570
[<ffffffffa0aa019e>] __x64_sys_mount+0x20e/0x280
[<ffffffffa1f47124>] do_syscall_64+0x34/0x80
[<ffffffffa200007e>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

unreferenced object 0xffff888108e71640 (size 64):
comm "fsmount", pid 7607, jiffies 4295044974 (age 1601.016s)
hex dump (first 32 bytes):
73 79 73 74 65 6d 5f 75 3a 6f 62 6a 65 63 74 5f system_u:object_
72 3a 74 65 73 74 5f 66 69 6c 65 73 79 73 74 65 r:test_filesyste
backtrace:
[<ffffffff861dc2b1>] memdup_user+0x21/0x90
[<ffffffff861dc367>] strndup_user+0x47/0xa0
[<ffffffff864f6965>] __do_sys_fsconfig+0x485/0x9f0
[<ffffffff87940124>] do_syscall_64+0x34/0x80
[<ffffffff87a0007e>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

Cc: stable@vger.kernel.org
Fixes: 70f4169ab421 ("selinux: parse contexts for mount options early")
Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
security/selinux/hooks.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)

--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2600,8 +2600,9 @@ static int selinux_sb_eat_lsm_opts(char
}
}
rc = selinux_add_opt(token, arg, mnt_opts);
+ kfree(arg);
+ arg = NULL;
if (unlikely(rc)) {
- kfree(arg);
goto free_opt;
}
} else {
@@ -2792,17 +2793,13 @@ static int selinux_fs_context_parse_para
struct fs_parameter *param)
{
struct fs_parse_result result;
- int opt, rc;
+ int opt;

opt = fs_parse(fc, selinux_fs_parameters, param, &result);
if (opt < 0)
return opt;

- rc = selinux_add_opt(opt, param->string, &fc->security);
- if (!rc)
- param->string = NULL;
-
- return rc;
+ return selinux_add_opt(opt, param->string, &fc->security);
}

/* inode security operations */