Re: [PATCH] tracing/kprobe: Fix NULL pointer access in trace_porbe_unlink()

[Masami Hiramatsu]

On Tue, 17 Sep 2019 08:56:43 -0400
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> On Tue, 17 Sep 2019 14:11:37 +0900
> Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
> 
> > Fix NULL pointer access in trace_probe_unlink() by initializing
> > trace_probe.list correctly in trace_probe_init().
> > 
> > In the error case of trace_probe_init(), it can call trace_probe_unlink()
> > before initializing trace_probe.list member. This causes NULL pointer
> > dereference at list_del_init() in trace_probe_unlink().
> > 
> > Syzbot reported :
> > 
> > kasan: CONFIG_KASAN_INLINE enabled
> > kasan: GPF could be caused by NULL-ptr deref or user memory access
> > general protection fault: 0000 [#1] PREEMPT SMP KASAN
> > CPU: 1 PID: 8633 Comm: syz-executor797 Not tainted 5.3.0-rc8-next-20190915
> > #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > RIP: 0010:__list_del_entry_valid+0x85/0xf5 lib/list_debug.c:51
> > Code: 0f 84 e1 00 00 00 48 b8 22 01 00 00 00 00 ad de 49 39 c4 0f 84 e2 00
> > 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 75
> > 53 49 8b 14 24 4c 39 f2 0f 85 99 00 00 00 49 8d 7d
> > RSP: 0018:ffff888090a7f9d8 EFLAGS: 00010246
> > RAX: dffffc0000000000 RBX: ffff88809b6f90c0 RCX: ffffffff817c0ca9
> > RDX: 0000000000000000 RSI: ffffffff817c0a73 RDI: ffff88809b6f90c8
> > RBP: ffff888090a7f9f0 R08: ffff88809a04e600 R09: ffffed1015d26aed
> > R10: ffffed1015d26aec R11: ffff8880ae935763 R12: 0000000000000000
> > R13: 0000000000000000 R14: ffff88809b6f90c0 R15: ffff88809b6f90d0
> > FS:  0000555556f99880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00000000006cc090 CR3: 00000000962b2000 CR4: 00000000001406e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >   __list_del_entry include/linux/list.h:131 [inline]
> >   list_del_init include/linux/list.h:190 [inline]
> >   trace_probe_unlink+0x1f/0x200 kernel/trace/trace_probe.c:959
> >   trace_probe_cleanup+0xd3/0x110 kernel/trace/trace_probe.c:973
> >   trace_probe_init+0x3f2/0x510 kernel/trace/trace_probe.c:1011
> >   alloc_trace_uprobe+0x5e/0x250 kernel/trace/trace_uprobe.c:353
> >   create_local_trace_uprobe+0x109/0x4a0 kernel/trace/trace_uprobe.c:1508
> >   perf_uprobe_init+0x131/0x210 kernel/trace/trace_event_perf.c:314
> >   perf_uprobe_event_init+0x106/0x1a0 kernel/events/core.c:8898
> >   perf_try_init_event+0x135/0x590 kernel/events/core.c:10184
> >   perf_init_event kernel/events/core.c:10228 [inline]
> >   perf_event_alloc.part.0+0x1b89/0x33d0 kernel/events/core.c:10505
> >   perf_event_alloc kernel/events/core.c:10887 [inline]
> >   __do_sys_perf_event_open+0xa2d/0x2d00 kernel/events/core.c:10989
> >   __se_sys_perf_event_open kernel/events/core.c:10871 [inline]
> >   __x64_sys_perf_event_open+0xbe/0x150 kernel/events/core.c:10871
> >   do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
> >   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > 
> > Reported-by: syzbot+2f807f4d3a2a4e87f18f@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Fixes: ca89bc071d5e ("tracing/kprobe: Add multi-probe per event support")
> > Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> 
> Thanks Masami. I was just about to get my pull request to Linus out,
> but will now add this and start running my tests with it.

Thanks Steve, and sorry, I found another issue on multiprobe. I'll send it soon.

Thank you,


-- 
Masami Hiramatsu <mhiramat@xxxxxxxxxx>