Re: [PATCH -next] tracing/osnoise: fix null-ptr-deref in bitmap_parselist

[Wang Liang]

在 2025/9/6 6:44, Steven Rostedt 写道:

On Fri, 5 Sep 2025 11:25:44 +0800
Wang Liang <wanglian...@huawei.com> wrote:

Hi Wang,

FYI, the tracincg subsystem requires capital subject:

   tracing/osnoise: Fix null-ptr-deref in bitmap_parselist()

And parenthesis for function names.

Thanks for your guide, it is clear and helpful!

A crash was observed with the following output:

BUG: kernel NULL pointer dereference, address: 0000000000000010
Oops: Oops: 0000 [#1] SMP NOPTI
CPU: 2 UID: 0 PID: 92 Comm: osnoise_cpus Not tainted 
6.17.0-rc4-00201-gd69eb204c255 #138 PREEMPT(voluntary)
RIP: 0010:bitmap_parselist+0x53/0x3e0
Call Trace:
  <TASK>
  osnoise_cpus_write+0x7a/0x190
  vfs_write+0xf8/0x410
  ? do_sys_openat2+0x88/0xd0
  ksys_write+0x60/0xd0
  do_syscall_64+0xa4/0x260
  entry_SYSCALL_64_after_hwframe+0x77/0x7f
  </TASK>

This issue can be reproduced by below code:

fd=open("/sys/kernel/debug/tracing/osnoise/cpus", O_WRONLY);
write(fd, "0-2", 0);

When user pass 'count=0' to osnoise_cpus_write(), kmalloc() will return
ZERO_SIZE_PTR (16) and cpulist_parse() treat it as a normal value, which
trigger the null pointer dereference. Add check for the parameter 'count'.

Fixes: 17f89102fe23 ("tracing/osnoise: Allow arbitrarily long CPU string")
Signed-off-by: Wang Liang <wanglian...@huawei.com>
---
  kernel/trace/trace_osnoise.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index fd259da0aa64..edf5178d0317 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -2322,6 +2322,9 @@ osnoise_cpus_write(struct file *filp, const char __user 
*ubuf, size_t count,
        int running, err;
        char *buf __free(kfree) = NULL;

+ if (count < 1)

+               return -EINVAL;

Sending a count of 0 is not invalid. This should simply return 0;

-- Steve

Ok. I will correct it and send a v2 patch later.

------
Best regards
Wang Liang

+
        buf = kmalloc(count, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;