Re: Unsafe access BufferDescriptors array in BufferGetLSNAtomic()

Xuneng Zhou <xunengzhou@gmail.com> 于2025年1月8日周三 13:35写道：

> Hi Tender,
>
> I’ve looked through the patch, and I believe there is a potential issue.
> The default size for BufferDescriptors appears to be 16,384. Passing and
> casting a negative buffer ID to a large unsigned integer in
> GetBufferDescriptor, and then using it as an array subscript, could
> potentially lead to an overflow.
>
> void
> BufferManagerShmemInit(void)
> {
>         bool            foundBufs,
>                                 foundDescs,
>                                 foundIOCV,
>                                 foundBufCkpt;
>
>         /* Align descriptors to a cacheline boundary. */
>         BufferDescriptors = (BufferDescPadded *)
>                 ShmemInitStruct("Buffer Descriptors",
>                                                 NBuffers *
> sizeof(BufferDescPadded),
>                                                 &foundDescs);
>
> int                     NBuffers = 16384;
>
> The changes proposed in the patch seem reasonable to me, but it might be
> helpful to include an explanation of the error case and how it’s handled.
>

Thanks for reviewing.
The  BufferGetLSNAtomic() with this patch looks not complex. I think no
need more explanation here.


> Best regards,
> [Xuneng]
>
> The new status of this patch is: Waiting on Author
>

I change the status to Ready for commiter
-- 
Thanks,
Tender Wang