On Wed 08-07-15 11:26:07, Steven Rostedt wrote:
> 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.
You're right. Thanks for catching this. I don't know what I was thinking
when writing that "fix"...
Honza
> 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 <rost...@goodmis.org>
> ---
> 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;
--
Jan Kara <j...@suse.cz>
SUSE Labs, CR
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