Re: [PATCH v2 1/4] misc: fastrpc: Add NULL check to fastrpc_buf_free to prevent crash

[Jianping <jianping.li@oss.qualcomm.com>]

On 1/16/2026 4:43 AM, Dmitry Baryshkov wrote:
> On Thu, Jan 15, 2026 at 04:28:48PM +0800, Jianping Li wrote:
>> From: Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>
>>
>> The fastrpc_buf_free function currently does not handle the case where
>> the input buffer pointer (buf) is NULL. This can lead to a null pointer
>> dereference, causing a crash or undefined behavior when the function
>> attempts to access members of the buf structure. Add a NULL check to
>> ensure safe handling of NULL pointers and prevent potential crashes.
> 
> When does it happen? Do you have a backtrace or is it a safety coding?
> Do you pass NULL buffer pointers to the function?
Thanks, Dmitry.
Yes, this change is mainly for safety‑coding purposes.

This is reachable on during remove/deinit sequences when a buffer was 
never allocated or allocation failed part‑way and cleanup proceeds.

It's a saftety coding: to eliminate NULL checks on the caller side, as 
we do in a lot of other kernel API.

At the same time, there is a possibility that this buffer passes NULL, 
and during verification, this can cause the kernel to crash.

The patch makes fastrpc_buf_free() NULL‑tolerant and simplifies callers 
by removing duplicated if (ptr) checks, reducing the chance of future 
omissions.
> 
>>
>> Fixes: c68cfb718c8f9 ("misc: fastrpc: Add support for context Invoke method")
>> Cc: stable@kernel.org
>> Co-developed-by: Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>
>> Signed-off-by: Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>
>> Signed-off-by: Jianping Li <jianping.li@oss.qualcomm.com>
>> ---
>>   drivers/misc/fastrpc.c | 12 ++++++------
>>   1 file changed, 6 insertions(+), 6 deletions(-)
>>
>