On Fri, 11 Jan 2019 22:45:59 +0900 Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > On Fri, 11 Jan 2019 07:01:13 +0100 > Andrea Righi <righi.andrea@xxxxxxxxx> wrote: > > > It is possible to trigger a NULL pointer dereference by writing an > > incorrectly formatted string to krpobe_events (trying to create a > > kretprobe omitting the symbol). > > > > Example: > > > > echo "r:event_1 " >> /sys/kernel/debug/tracing/kprobe_events > > > > That triggers this: > > > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 > > #PF error: [normal kernel read fault] > > PGD 0 P4D 0 > > Oops: 0000 [#1] SMP PTI > > CPU: 6 PID: 1757 Comm: bash Not tainted 5.0.0-rc1+ #125 > > Hardware name: Dell Inc. XPS 13 9370/0F6P3V, BIOS 1.5.1 08/09/2018 > > RIP: 0010:kstrtoull+0x2/0x20 > > Code: 28 00 00 00 75 17 48 83 c4 18 5b 41 5c 5d c3 b8 ea ff ff ff eb e1 b8 de ff ff ff eb da e8 d6 36 bb ff 66 0f 1f 44 00 00 31 c0 <80> 3f 2b 55 48 89 e5 0f 94 c0 48 01 c7 e8 5c ff ff ff 5d c3 66 2e > > RSP: 0018:ffffb5d482e57cb8 EFLAGS: 00010246 > > RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff82b12720 > > RDX: ffffb5d482e57cf8 RSI: 0000000000000000 RDI: 0000000000000000 > > RBP: ffffb5d482e57d70 R08: ffffa0c05e5a7080 R09: ffffa0c05e003980 > > R10: 0000000000000000 R11: 0000000040000000 R12: ffffa0c04fe87b08 > > R13: 0000000000000001 R14: 000000000000000b R15: ffffa0c058d749e1 > > FS: 00007f137c7f7740(0000) GS:ffffa0c05e580000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 0000000000000000 CR3: 0000000497d46004 CR4: 00000000003606e0 > > Call Trace: > > ? trace_kprobe_create+0xb6/0x840 > > ? _cond_resched+0x19/0x40 > > ? _cond_resched+0x19/0x40 > > ? __kmalloc+0x62/0x210 > > ? argv_split+0x8f/0x140 > > ? trace_kprobe_create+0x840/0x840 > > ? trace_kprobe_create+0x840/0x840 > > create_or_delete_trace_kprobe+0x11/0x30 > > trace_run_command+0x50/0x90 > > trace_parse_run_command+0xc1/0x160 > > probes_write+0x10/0x20 > > __vfs_write+0x3a/0x1b0 > > ? apparmor_file_permission+0x1a/0x20 > > ? security_file_permission+0x31/0xf0 > > ? _cond_resched+0x19/0x40 > > vfs_write+0xb1/0x1a0 > > ksys_write+0x55/0xc0 > > __x64_sys_write+0x1a/0x20 > > do_syscall_64+0x5a/0x120 > > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > > Fix by doing the proper argument checks in trace_kprobe_create(). > > Thank you Andrea! > > Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx> > I've applied it and will be testing it now. Thanks! -- Steve
