From 6f02c6b196036dbb6defb4647d8707d29b7fe95b Mon Sep 17 00:00:00 2001 From: Tom Ryan Date: Mon, 9 Mar 2026 22:20:02 -0700 Subject: [PATCH] io_uring: fix physical SQE bounds check for SQE_MIXED 128-byte ops When IORING_SETUP_SQE_MIXED is used without IORING_SETUP_NO_SQARRAY, the boundary check for 128-byte SQE operations in io_init_req() validated the logical SQ head position rather than the physical SQE index. The existing check: !(ctx->cached_sq_head & (ctx->sq_entries - 1)) ensures the logical position isn't at the end of the ring, which is correct for NO_SQARRAY rings where physical == logical. However, when sq_array is present, an unprivileged user can remap any logical position to an arbitrary physical index via sq_array. Setting sq_array[N] = sq_entries - 1 places a 128-byte operation at the last physical SQE slot, causing the 128-byte memcpy in io_uring_cmd_sqe_copy() to read 64 bytes past the end of the SQE array. Replace the cached_sq_head alignment check with a direct validation of the physical SQE index, which correctly handles both sq_array and NO_SQARRAY cases. Fixes: 1cba30bf9fdd ("io_uring: add support for IORING_SETUP_SQE_MIXED") Signed-off-by: Tom Ryan Link: https://patch.msgid.link/20260310052003.72871-1-ryan36005@gmail.com Signed-off-by: Jens Axboe --- io_uring/io_uring.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 20fdc442e014..20ec8fdafcae 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -1745,7 +1745,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req, * well as 2 contiguous entries. */ if (!(ctx->flags & IORING_SETUP_SQE_MIXED) || *left < 2 || - !(ctx->cached_sq_head & (ctx->sq_entries - 1))) + (unsigned)(sqe - ctx->sq_sqes) >= ctx->sq_entries - 1) return io_init_fail_req(req, -EINVAL); /* * A 128b operation on a mixed SQ uses two entries, so we have