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

[Greg KH <gregkh@linuxfoundation.org>]

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?

thanks,

greg k-h