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().
Link: https://lore.kernel.org/lkml/[email protected]
Fixes: 6212dd29683e ("tracing/kprobes: Use dyn_event framework for kprobe events")
Cc: [email protected]
Signed-off-by: Andrea Righi <[email protected]>
Signed-off-by: Masami Hiramatsu <[email protected]>
---
v2: argument check refactoring
kernel/trace/trace_kprobe.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 5c19b8c41c7e..d5fb09ebba8b 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -607,11 +607,17 @@ static int trace_kprobe_create(int argc, const char *argv[])
char buf[MAX_EVENT_NAME_LEN];
unsigned int flags = TPARG_FL_KERNEL;
- /* argc must be >= 1 */
- if (argv[0][0] == 'r') {
+ switch (argv[0][0]) {
+ case 'r':
is_return = true;
flags |= TPARG_FL_RETURN;
- } else if (argv[0][0] != 'p' || argc < 2)
+ break;
+ case 'p':
+ break;
+ default:
+ return -ECANCELED;
+ }
+ if (argc < 2)
return -ECANCELED;
event = strchr(&argv[0][1], ':');
--
2.17.1
On Fri, 11 Jan 2019 07:01:13 +0100
Andrea Righi <[email protected]> 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 <[email protected]>
>
> Link: https://lore.kernel.org/lkml/[email protected]
> Fixes: 6212dd29683e ("tracing/kprobes: Use dyn_event framework for kprobe events")
> Cc: [email protected]
> Signed-off-by: Andrea Righi <[email protected]>
> Signed-off-by: Masami Hiramatsu <[email protected]>
> ---
> v2: argument check refactoring
>
> kernel/trace/trace_kprobe.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 5c19b8c41c7e..d5fb09ebba8b 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -607,11 +607,17 @@ static int trace_kprobe_create(int argc, const char *argv[])
> char buf[MAX_EVENT_NAME_LEN];
> unsigned int flags = TPARG_FL_KERNEL;
>
> - /* argc must be >= 1 */
> - if (argv[0][0] == 'r') {
> + switch (argv[0][0]) {
> + case 'r':
> is_return = true;
> flags |= TPARG_FL_RETURN;
> - } else if (argv[0][0] != 'p' || argc < 2)
> + break;
> + case 'p':
> + break;
> + default:
> + return -ECANCELED;
> + }
> + if (argc < 2)
> return -ECANCELED;
>
> event = strchr(&argv[0][1], ':');
> --
> 2.17.1
>
--
Masami Hiramatsu <[email protected]>
On Fri, 11 Jan 2019 22:45:59 +0900
Masami Hiramatsu <[email protected]> wrote:
> On Fri, 11 Jan 2019 07:01:13 +0100
> Andrea Righi <[email protected]> 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 <[email protected]>
>
I've applied it and will be testing it now. Thanks!
-- Steve
On Fri, 11 Jan 2019 07:01:13 +0100
Andrea Righi <[email protected]> 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().
>
> Link: https://lore.kernel.org/lkml/[email protected]
> Fixes: 6212dd29683e ("tracing/kprobes: Use dyn_event framework for kprobe events")
> Cc: [email protected]
Dropping the stable tag because it appears that the Fixes commit went
into 5.0-rc1, which there's no stable kernel for.
-- Steve
> Signed-off-by: Andrea Righi <[email protected]>
> Signed-off-by: Masami Hiramatsu <[email protected]>
> ---