diff options
| author | Yousef Alhouseen <alhouseenyousef@gmail.com> | 2026-06-30 23:18:27 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2026-07-02 06:25:21 -0600 |
| commit | f01f5275feb77bac9fefbbf7cc584fe0b3850a92 (patch) | |
| tree | d1d9638c2e78a4c30add35c26c2d9d93c7d9b6d8 | |
| parent | 1e56f30a73f304fe26a272742c398aedd88a1a6c (diff) | |
ublk: snapshot batch commands before preparing I/O
The batch prepare path rereads its userspace element array when rolling
back a partially prepared batch. Userspace can change an already
processed tag before the second read, causing rollback to reject the
replacement tag and leave earlier I/O slots prepared. The
WARN_ON_ONCE() in the rollback path then fires.
Copy the bounded batch into kernel memory before changing any I/O state
and use the same snapshot for preparation and rollback. Commit and fetch
batches retain the existing chunked userspace walk.
Fixes: b256795b3606 ("ublk: handle UBLK_U_IO_PREP_IO_CMDS")
Reported-by: syzbot+1a67ee1aa79484801ec6@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=1a67ee1aa79484801ec6
Signed-off-by: Yousef Alhouseen <alhouseenyousef@gmail.com>
Reviewed-by: Ming Lei <tom.leiming@gmail.com>
Link: https://patch.msgid.link/20260630211827.50475-1-alhouseenyousef@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | drivers/block/ublk_drv.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index 4f6d9e652187..c2c11f2a01e7 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -3584,6 +3584,7 @@ ublk_batch_auto_buf_reg(const struct ublk_batch_io *uc, #define UBLK_CMD_BATCH_TMP_BUF_SZ (48 * 10) struct ublk_batch_io_iter { void __user *uaddr; + const u8 *kaddr; unsigned done, total; unsigned char elem_bytes; /* copy to this buffer from user space */ @@ -3632,7 +3633,10 @@ static int ublk_walk_cmd_buf(struct ublk_batch_io_iter *iter, while (iter->done < iter->total) { unsigned int len = min(sizeof(iter->buf), iter->total - iter->done); - if (copy_from_user(iter->buf, iter->uaddr + iter->done, len)) { + if (iter->kaddr) { + memcpy(iter->buf, iter->kaddr + iter->done, len); + } else if (copy_from_user(iter->buf, iter->uaddr + iter->done, + len)) { pr_warn("ublk%d: read batch cmd buffer failed\n", data->ub->dev_info.dev_id); return -EFAULT; @@ -3723,14 +3727,21 @@ static int ublk_handle_batch_prep_cmd(const struct ublk_batch_io_data *data) .total = uc->nr_elem * uc->elem_bytes, .elem_bytes = uc->elem_bytes, }; + void *cmd_buf; int ret; + cmd_buf = vmemdup_user(iter.uaddr, iter.total); + if (IS_ERR(cmd_buf)) + return PTR_ERR(cmd_buf); + iter.kaddr = cmd_buf; + mutex_lock(&data->ub->mutex); ret = ublk_walk_cmd_buf(&iter, data, ublk_batch_prep_io); if (ret && iter.done) ublk_batch_revert_prep_cmd(&iter, data); mutex_unlock(&data->ub->mutex); + kvfree(cmd_buf); return ret; } |