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io_uring: improve import_fixed overflow checks 

Replace a hand-coded overflow check with a specialised function. Even
though compilers are smart enough to generate identical binary (i.e.
check carry bit), but it's more foolproof and conveys the intention
better.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/e437dcdc929bacbb6f11a4824ecbbf17225cb82a.1617287883.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-04-01 15:43:54 +01:00 committed by Jens Axboe
parent 0aec38fda2
commit 75769e3f73
1 changed files with 3 additions and 4 deletions
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7
fs/io_uring.c
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@ -2785,8 +2785,8 @@ static int io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter)
size_t len = req->rw.len;
struct io_mapped_ubuf *imu;
u16 index, buf_index = req->buf_index;
u64 buf_end, buf_addr = req->rw.addr;
size_t offset;
u64 buf_addr;
if (unlikely(buf_index >= ctx->nr_user_bufs))
return -EFAULT;
@ -2794,11 +2794,10 @@ static int io_import_fixed(struct io_kiocb *req, int rw, struct iov_iter *iter)
imu = &ctx->user_bufs[index];
buf_addr = req->rw.addr;
/* overflow */
if (buf_addr + len < buf_addr)
if (unlikely(check_add_overflow(buf_addr, (u64)len, &buf_end)))
return -EFAULT;
/* not inside the mapped region */
if (buf_addr < imu->ubuf || buf_addr + len > imu->ubuf + imu->len)
if (buf_addr < imu->ubuf || buf_end > imu->ubuf + imu->len)
return -EFAULT;
/*