[PATCH] tracing: kprobe-event: Fix null-ptr-deref in trace_kprobe_create_internal()

[PATCH] tracing: kprobe-event: Fix null-ptr-deref in trace_kprobe_create_internal()

[Wang Liang]

A crash was observed with the following output:

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 UID: 0 PID: 2899 Comm: syz.2.399 Not tainted 6.17.0-rc5+ #5 PREEMPT(none)
RIP: 0010:trace_kprobe_create_internal+0x3fc/0x1440 kernel/trace/trace_kprobe.c:911
Call Trace:
 <TASK>
 trace_kprobe_create_cb+0xa2/0xf0 kernel/trace/trace_kprobe.c:1089
 trace_probe_create+0xf1/0x110 kernel/trace/trace_probe.c:2246
 dyn_event_create+0x45/0x70 kernel/trace/trace_dynevent.c:128
 create_or_delete_trace_kprobe+0x5e/0xc0 kernel/trace/trace_kprobe.c:1107
 trace_parse_run_command+0x1a5/0x330 kernel/trace/trace.c:10785
 vfs_write+0x2b6/0xd00 fs/read_write.c:684
 ksys_write+0x129/0x240 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x5d/0x2d0 arch/x86/entry/syscall_64.c:94
 </TASK>

Function kmemdup() may return NULL in trace_kprobe_create_internal(), add
check for it's return value.

Fixes: 33b4e38baa03 ("tracing: kprobe-event: Allocate string buffers from heap")
Signed-off-by: Wang Liang <wangliang74@huawei.com>
---
 kernel/trace/trace_kprobe.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index ccae62d4fb91..fa60362a3f31 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -908,6 +908,8 @@ static int trace_kprobe_create_internal(int argc, const char *argv[],
 			return -EINVAL;
 		}
 		buf = kmemdup(&argv[0][1], len + 1, GFP_KERNEL);
+		if (!buf)
+			return -ENOMEM;
 		buf[len] = '\0';
 		ret = kstrtouint(buf, 0, &maxactive);
 		if (ret || !maxactive) {
-- 
2.34.1

Re: [PATCH] tracing: kprobe-event: Fix null-ptr-deref in trace_kprobe_create_internal()

[Masami Hiramatsu]

On Tue, 16 Sep 2025 15:58:16 +0800
Wang Liang <wangliang74@huawei.com> wrote:

> A crash was observed with the following output:
> 
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> CPU: 1 UID: 0 PID: 2899 Comm: syz.2.399 Not tainted 6.17.0-rc5+ #5 PREEMPT(none)
> RIP: 0010:trace_kprobe_create_internal+0x3fc/0x1440 kernel/trace/trace_kprobe.c:911
> Call Trace:
>  <TASK>
>  trace_kprobe_create_cb+0xa2/0xf0 kernel/trace/trace_kprobe.c:1089
>  trace_probe_create+0xf1/0x110 kernel/trace/trace_probe.c:2246
>  dyn_event_create+0x45/0x70 kernel/trace/trace_dynevent.c:128
>  create_or_delete_trace_kprobe+0x5e/0xc0 kernel/trace/trace_kprobe.c:1107
>  trace_parse_run_command+0x1a5/0x330 kernel/trace/trace.c:10785
>  vfs_write+0x2b6/0xd00 fs/read_write.c:684
>  ksys_write+0x129/0x240 fs/read_write.c:738
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0x5d/0x2d0 arch/x86/entry/syscall_64.c:94
>  </TASK>
> 
> Function kmemdup() may return NULL in trace_kprobe_create_internal(), add
> check for it's return value.

Oops, thanks for fixing!
Let me pick this!

> 
> Fixes: 33b4e38baa03 ("tracing: kprobe-event: Allocate string buffers from heap")
> Signed-off-by: Wang Liang <wangliang74@huawei.com>
> ---
>  kernel/trace/trace_kprobe.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index ccae62d4fb91..fa60362a3f31 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -908,6 +908,8 @@ static int trace_kprobe_create_internal(int argc, const char *argv[],
>  			return -EINVAL;
>  		}
>  		buf = kmemdup(&argv[0][1], len + 1, GFP_KERNEL);
> +		if (!buf)
> +			return -ENOMEM;
>  		buf[len] = '\0';
>  		ret = kstrtouint(buf, 0, &maxactive);
>  		if (ret || !maxactive) {
> -- 
> 2.34.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>