Re: [PATCH 1/2] tracing/uprobe: Fix NULL pointer dereference in trace_uprobe_create()

[Masami Hiramatsu]

On Fri, 14 Jun 2019 16:40:25 +0900
Eiichi Tsukata <devel@xxxxxxxxxxxx> wrote:

> Just like the case of commit 8b05a3a7503c ("tracing/kprobes: Fix NULL
> pointer dereference in trace_kprobe_create()"), writing an incorrectly
> formatted string to uprobe_events can trigger NULL pointer dereference.
> 
> Reporeducer:
> 
>   # echo r > /sys/kernel/debug/tracing/uprobe_events
> 
> dmesg:
> 
>   BUG: kernel NULL pointer dereference, address: 0000000000000000
>   #PF: supervisor read access in kernel mode
>   #PF: error_code(0x0000) - not-present page
>   PGD 8000000079d12067 P4D 8000000079d12067 PUD 7b7ab067 PMD 0
>   Oops: 0000 [#1] PREEMPT SMP PTI
>   CPU: 0 PID: 1903 Comm: bash Not tainted 5.2.0-rc3+ #15
>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-2.fc30 04/01/2014
>   RIP: 0010:strchr+0x0/0x30
>   Code: c0 eb 0d 84 c9 74 18 48 83 c0 01 48 39 d0 74 0f 0f b6 0c 07 3a 0c 06 74 ea 19 c0 83 c8 01 c3 31 c0 c3 0f 1f 84 00 00 00 00 00 <0f> b6 07 89 f2 40 38 f0 75 0e eb 13 0f b6 47 01 48 83 c
>   RSP: 0018:ffffb55fc0403d10 EFLAGS: 00010293
> 
>   RAX: ffff993ffb793400 RBX: 0000000000000000 RCX: ffffffffa4852625
>   RDX: 0000000000000000 RSI: 000000000000002f RDI: 0000000000000000
>   RBP: ffffb55fc0403dd0 R08: ffff993ffb793400 R09: 0000000000000000
>   R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
>   R13: ffff993ff9cc1668 R14: 0000000000000001 R15: 0000000000000000
>   FS:  00007f30c5147700(0000) GS:ffff993ffda00000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 0000000000000000 CR3: 000000007b628000 CR4: 00000000000006f0
>   Call Trace:
>    trace_uprobe_create+0xe6/0xb10
>    ? __kmalloc_track_caller+0xe6/0x1c0
>    ? __kmalloc+0xf0/0x1d0
>    ? trace_uprobe_create+0xb10/0xb10
>    create_or_delete_trace_uprobe+0x35/0x90
>    ? trace_uprobe_create+0xb10/0xb10
>    trace_run_command+0x9c/0xb0
>    trace_parse_run_command+0xf9/0x1eb
>    ? probes_open+0x80/0x80
>    __vfs_write+0x43/0x90
>    vfs_write+0x14a/0x2a0
>    ksys_write+0xa2/0x170
>    do_syscall_64+0x7f/0x200
>    entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Fixes: 0597c49c69d5 ("tracing/uprobes: Use dyn_event framework for uprobe events")
> Signed-off-by: Eiichi Tsukata <devel@xxxxxxxxxxxx>

Sorry, I missed this fix.

Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>

Steve, could you pick this as an urgent fix?

Thank you!

> ---
>  kernel/trace/trace_uprobe.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 0d60d6856de5..7dc8ee55cf84 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -443,10 +443,17 @@ static int trace_uprobe_create(int argc, const char **argv)
>  	ret = 0;
>  	ref_ctr_offset = 0;
>  
> -	/* argc must be >= 1 */
> -	if (argv[0][0] == 'r')
> +	switch (argv[0][0]) {
> +	case 'r':
>  		is_return = true;
> -	else if (argv[0][0] != 'p' || argc < 2)
> +		break;
> +	case 'p':
> +		break;
> +	default:
> +		return -ECANCELED;
> +	}
> +
> +	if (argc < 2)
>  		return -ECANCELED;
>  
>  	if (argv[0][1] == ':')
> -- 
> 2.21.0
> 


-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>