Re: [PATCH] RDMA/rxe: validate cur_sge on the receive path before indexing dma->sge[]

[Zhu Yanjun <yanjun.zhu@linux.dev>]

在 2026/9/30 8:34, Greg KH 写道:
> On Thu, Oct 01, 2026 at 12:15:52AM +0900, AYS wrote:
>> A user QP's receive queue is an mmap'd ring: the user provider writes the
>> WQEs and post_recv does not touch them, so every field of struct
>> rxe_recv_wqe is attacker controlled. When the responder takes a WQE it
>> validates only dma.num_sge (rxe_get_recv_wqe()/get_srq_wqe()); dma.cur_sge,
>> dma.sge_offset and dma.resid are copied into qp->resp.srq_wqe unchecked.
>>
>> copy_data() then uses cur_sge as an index immediately --
>> struct rxe_sge *sge = &dma->sge[dma->cur_sge];
>> -- and dereferences it (sge->length) before the in-loop
>> "dma->cur_sge >= dma->num_sge" test, which only runs after the first sge++.
>> cur_sge is a u32, so this reads far out of bounds of the RXE_MAX_SGE-entry
>> dma->sge[] embedded in the kmalloc-2k struct rxe_qp: an information leak (the
>> out-of-bounds sge->length is recoverable through the work-completion status)
>> and a DoS. The send queue already got this check in commit 126c757e4cd4; the
>> receive path did not.
>>
>> Reject an out-of-range cur_sge in copy_data() before the first sge
>> dereference. This also covers the send retry path and is harmless to the
>> kernel ULP path, which always sets cur_sge = 0.
>>
>> Fixes: 8700e3e7c485 ("Soft RoCE driver")
>> Signed-off-by: Youngsung Ahn <ays511.kr@gmail.com>
> 
> Does not match the "From:" line :(
> 
> No cc: stable?
> 
> No Assisted-by: line?

In v2, this Assisted-by tag has been added.

Yanjun Zhu>
> thanks,
> 
> greg k-h