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io_uring: fix NULL reg-buffer

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io_import_fixed() doesn't expect a registered buffer slot to be NULL and
would fail stumbling on it. We don't allow it, but if during
__io_sqe_buffers_update() rsrc removal succeeds but following register
fails, we'll get such a situation.

Do it atomically and don't remove buffers until we sure that a new one
can be set.

Fixes: 634d00df5e ("io_uring: add full-fledged dynamic buffers support")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/830020f9c387acddd51962a3123b5566571b8c6d.1619446608.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-04-26 15:17:38 +01:00 committed by Jens Axboe
parent 9f59a9d88d
commit 0b8c0e7c96
1 changed files with 17 additions and 17 deletions
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34
fs/io_uring.c
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@ -8419,7 +8419,6 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
{
u64 __user *tags = u64_to_user_ptr(up->tags);
struct iovec iov, __user *iovs = u64_to_user_ptr(up->data);
struct io_mapped_ubuf *imu;
struct page *last_hpage = NULL;
bool needs_switch = false;
__u32 done;
@ -8431,6 +8430,8 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
return -EINVAL;
for (done = 0; done < nr_args; done++) {
struct io_mapped_ubuf *imu;
int offset = up->offset + done;
u64 tag = 0;
err = io_copy_iov(ctx, &iov, iovs, done);
@ -8440,28 +8441,27 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
err = -EFAULT;
break;
}
err = io_buffer_validate(&iov);
if (err)
break;
err = io_sqe_buffer_register(ctx, &iov, &imu, &last_hpage);
if (err)
break;
i = array_index_nospec(up->offset + done, ctx->nr_user_bufs);
imu = ctx->user_bufs[i];
if (imu) {
err = io_queue_rsrc_removal(ctx->buf_data, up->offset + done,
ctx->rsrc_node, imu);
if (err)
i = array_index_nospec(offset, ctx->nr_user_bufs);
if (ctx->user_bufs[i]) {
err = io_queue_rsrc_removal(ctx->buf_data, offset,
ctx->rsrc_node, ctx->user_bufs[i]);
if (unlikely(err)) {
io_buffer_unmap(ctx, &imu);
break;
}
ctx->user_bufs[i] = NULL;
needs_switch = true;
}
if (iov.iov_base || iov.iov_len) {
err = io_buffer_validate(&iov);
if (err)
break;
err = io_sqe_buffer_register(ctx, &iov, &ctx->user_bufs[i],
&last_hpage);
if (err)
break;
ctx->buf_data->tags[up->offset + done] = tag;
}
ctx->user_bufs[i] = imu;
ctx->buf_data->tags[offset] = tag;
}
if (needs_switch)