[PATCH 6.18 005/686] nvmet-rdma: fix out-of-bounds write in nvmet_rdma_map_sgl_inline()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrew Stellman <astellman@stellman-greene.com>

[ Upstream commit d1512773a0d539669440bd9f6d050b8e12923b5f ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/nvme/target/rdma.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
index a0ba6641c7ffb..ae44a0ff34d74 100644
--- a/drivers/nvme/target/rdma.c
+++ b/drivers/nvme/target/rdma.c
@@ -864,7 +864,8 @@ static u16 nvmet_rdma_map_sgl_inline(struct nvmet_rdma_rsp *rsp)
 		return NVME_SC_INVALID_FIELD | NVME_STATUS_DNR;
 	}
 
-	if (off + len > rsp->queue->dev->inline_data_size) {
+	if (off > (u64)rsp->queue->dev->inline_data_size ||
+	    len > (u64)rsp->queue->dev->inline_data_size - off) {
 		pr_err("invalid inline data offset!\n");
 		return NVME_SC_SGL_INVALID_OFFSET | NVME_STATUS_DNR;
 	}
-- 
2.53.0