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io_uring/fdinfo: fix OOB read in SQE_MIXED wrap check 

__io_uring_show_fdinfo() iterates over pending SQEs and, for 128-byte
SQEs on an IORING_SETUP_SQE_MIXED ring, needs to detect when the second
half of the SQE would be past the end of the sq_sqes array. The current
check tests (++sq_head & sq_mask) == 0, but sq_head is only incremented
when a 128-byte SQE is encountered, not on every iteration. The actual
array index is sq_idx = (i + sq_head) & sq_mask, which can be sq_mask
(the last slot) while the wrap check passes.

Fix by checking sq_idx directly. Keep the sq_head increment so the loop
still skips the second half of the 128-byte SQE on the next iteration.

Fixes: 1cba30bf9f ("io_uring: add support for IORING_SETUP_SQE_MIXED")
Signed-off-by: Nicholas Carlini <nicholas@carlini.com>
Link: https://patch.msgid.link/20260327021823.3138396-1-nicholas@carlini.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Nicholas Carlini 2026-03-27 02:18:23 +00:00 committed by Jens Axboe
parent b59efde9e6
commit 5170efd9c3
1 changed files with 2 additions and 1 deletions
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3
io_uring/fdinfo.c
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@ -119,12 +119,13 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
sq_idx);
break;
}
if ((++sq_head & sq_mask) == 0) {
if (sq_idx == sq_mask) {
seq_printf(m,
"%5u: corrupted sqe, wrapping 128B entry\n",
sq_idx);
break;
}
sq_head++;
i++;
sqe128 = true;
}