Re: [PATCH v2 2/2] mmc: block: Let MMC_IOC_MULTI_CMD return zero again for zero entries
From: Ulf Hansson
Date: Tue Jul 11 2017 - 10:44:50 EST
On 5 July 2017 at 17:09, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> With gcc 4.1.2:
> drivers/mmc/core/block.c: In function âmmc_blk_ioctl_cmd_issueâ:
> drivers/mmc/core/block.c:630: warning: âioc_errâ may be used uninitialized in this function
> Indeed, if mq_rq->ioc_count is zero, an uninitialized value will be
> stored in mq_rq->drv_op_result and passed to blk_end_request_all().
> Can mq_rq->ioc_count be zero?
> - mmc_blk_ioctl_cmd() sets ioc_count to 1, so this is safe,
> - mmc_blk_ioctl_multi_cmd() obtains ioc_count from user space in
> response to the MMC_IOC_MULTI_CMD ioctl, and does allow zero.
> To avoid returning an uninitialized value, and as it is pointless to do
> all this work when the MMC_IOC_MULTI_CMD ioctl is used with zero
> entries, check for this early in mmc_blk_ioctl_multi_cmd(), and return
> zero, like was returned before.
> Fixes: 3ecd8cf23f88d5df ("mmc: block: move multi-ioctl() to use block layer")
> Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Thanks, applied for fixes!
> Should mmc_blk_ioctl_multi_cmd() return -EINVAL instead for this case?
> That would change behavior as seen from userspace, though.
> Feel free to fold in the previous patch if deemed appropriate.
> - No changes.
> drivers/mmc/core/block.c | 3 +++
> 1 file changed, 3 insertions(+)
> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> index 4920ea1ece38a9b6..e0363223996e6096 100644
> --- a/drivers/mmc/core/block.c
> +++ b/drivers/mmc/core/block.c
> @@ -637,6 +637,9 @@ static int mmc_blk_ioctl_multi_cmd(struct block_device *bdev,
> return -EFAULT;
> + if (!num_of_cmds)
> + return 0;
> if (num_of_cmds > MMC_IOC_MAX_CMDS)
> return -EINVAL;