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io_uring/kbuf: Fix check of BID wrapping in provided buffers

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Commit 3851d25c75 ("io_uring: check for rollover of buffer ID when
providing buffers") introduced a check to prevent wrapping the BID
counter when sqe->off is provided, but it's off-by-one too
restrictive, rejecting the last possible BID (65534).

i.e., the following fails with -EINVAL.

     io_uring_prep_provide_buffers(sqe, addr, size, 0xFFFF, 0, 0);

Fixes: 3851d25c75 ("io_uring: check for rollover of buffer ID when providing buffers")
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
Link: https://lore.kernel.org/r/20231005000531.30800-2-krisman@suse.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Gabriel Krisman Bertazi 2023-10-04 20:05:29 -04:00 committed by Jens Axboe
parent 922a2c78f1
commit ab69838e7c
1 changed files with 1 additions and 1 deletions
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2
io_uring/kbuf.c
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@ -352,7 +352,7 @@ int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
tmp = READ_ONCE(sqe->off);
if (tmp > USHRT_MAX)
return -E2BIG;
if (tmp + p->nbufs >= USHRT_MAX)
if (tmp + p->nbufs > USHRT_MAX)
return -EINVAL;
p->bid = tmp;
return 0;