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'.
Link:
https://lore.kernel.org/all/20250905032544.231962-1-wanglian...@huawei.com/
Fixes: 17f89102fe23 ("tracing/osnoise: Allow arbitrarily long CPU string")
Signed-off-by: Wang Liang <wanglian...@huawei.com>
---
v2: return 0 when sending a count of 0.
---
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..337bc0eb5d71 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 0;
+
buf = kmalloc(count, GFP_KERNEL);
if (!buf)
return -ENOMEM;
--
2.34.1
