When testing 4.2-rc1 I hit this WARNING:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 1639 at
/work/autotest/nobackup/linux-test.git/kernel/auditsc.c:1025
audit_log_exit+0x734/0xb0d()
Modules linked in:
CPU: 1 PID: 1639 Comm: fstab-decode Not tainted 4.2.0-rc1-test+ #2
Hardware name: MSI MS-7823/CSM-H87M-G43 (MS-7823), BIOS V1.6 02/22/2014
00000000 00000000 f0817eb4 c0cd118d c10224d4 f0817ee4 c0440fbe c1011b30
00000001 00000667 c10224d4 00000401 c04ba081 c04ba081 f18e3c00 f1cd5080^M
00000000 f0817ef4 c0440ff7 00000009 00000000 f0817f84 c04ba081 f0817f60
Call Trace:
[<c0cd118d>] dump_stack+0x41/0x52
[<c0440fbe>] warn_slowpath_common+0x9d/0xb4
[<c04ba081>] ? audit_log_exit+0x734/0xb0d
[<c04ba081>] ? audit_log_exit+0x734/0xb0d
[<c0440ff7>] warn_slowpath_null+0x22/0x24
[<c04ba081>] audit_log_exit+0x734/0xb0d
[<c04bb7f4>] __audit_syscall_exit+0x43/0xf6
[<c040ce27>] syscall_trace_leave+0x30/0xe5
[<c0cdbced>] syscall_exit_work+0x19/0x1e
---[ end trace 156b2a7afa592deb ]---
Debugging it, I found that it was triggered by this commit:
commit 0b08c5e5944 ("audit: Fix check of return value of strnlen_user()")
Yes, strnlen_user() returns 0 on fault, but if you look at what len is
set to, than you would notice that on fault len would be -1.
len = strnlen_user(p, MAX_ARG_STRLEN) - 1;
Now the warning triggers on a string of size zero ("\0"), which is a
legitimate entry.
Signed-off-by: Steven Rostedt <[email protected]>
---
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 09c65640cad6..ee097948b0a8 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1021,7 +1021,7 @@ static int audit_log_single_execve_arg(struct
audit_context *context,
* for strings that are too long, we should not have created
* any.
*/
- if (unlikely((len == 0) || len > MAX_ARG_STRLEN - 1)) {
+ if (unlikely((len == -1) || len > MAX_ARG_STRLEN - 1)) {
WARN_ON(1);
send_sig(SIGKILL, current, 0);
return -1;
--
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