nvmet-rdma: fix out-of-bounds write in nvmet_rdma_map_sgl_inline()

nvmet_rdma_map_sgl_inline() bounds the host-supplied in-capsule SGL
offset with "off + len > inline_data_size", evaluated in 64-bit
arithmetic. off is taken straight from the host SGL descriptor
(le64_to_cpu(sgl->addr)) and len is promoted to 64-bit, so the sum
wraps: an off within len of 2^64 makes it small and the check passes.
off is then used as page_idx = off / PAGE_SIZE to index the fixed-size
rsp->cmd->inline_sg[] array (NVMET_RDMA_MAX_INLINE_SGE entries), so a
crafted offset yields an out-of-bounds scatterlist index that is written
through in nvmet_rdma_use_inline_sg().

The mapping runs while handling a received capsule, before the command
executes, so a remote RDMA peer can reach it (the Connect capsule is a
write and takes this path on a queue that has no controller yet). The
host controls only the low bits of the resulting displacement, so the
expected impact is an out-of-bounds write that faults the target
(remote denial of service).

This wrap was reported, with a KASAN reproduction, on linux-nvme in May,
and the check below was suggested in that thread. The fix that was
applied, 48c0162f647b, reworked how the offset is mapped but kept the
original check, and its page index turns a wrapped offset into an
out-of-bounds index into inline_sg[].

Reject the offset before it can wrap.

Found independently by static analysis with AI assistance, not
reproduced at runtime.

Fixes: 0d5ee2b2ab4f ("nvmet-rdma: support max(16KB, PAGE_SIZE) inline data")
Fixes: 48c0162f647b ("nvmet-rdma: handle inline data with a nonzero offset")
Reported-by: Bryam Vargas <hexlabsecurity@proton.me>
Closes: https://lore.kernel.org/all/LM21QIR-1-qJb7PViyJKCnGBnUzizeiNJVWQ3wb7ZwGezodjgKg3f-iobqOyequ-sT1jFCKJImfqNO_BKU3KO80xFITnaI5GTV_GxLUNDDc=@proton.me/
Suggested-by: Keith Busch <kbusch@kernel.org>
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5
Signed-off-by: Andrew Stellman <astellman@stellman-greene.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

0 files changed, 0 insertions, 0 deletions