mmc: block: fix ABI regression of mmc_blk_ioctl

If mmc_blk_ioctl returns -EINVAL, blkdev_ioctl continues to
work without returning err to user-space. But now we check
CAP_SYS_RAWIO firstly, so we return -EPERM to blkdev_ioctl,
which make blkdev_ioctl return -EPERM to user-space directly.
So this will break all the ioctl with BLKROSET. Now we find
Android-adb suffer it for the following log:

remount of /system failed;
couldn't make block device writable: Operation not permitted
openat(AT_FDCWD, "/dev/block/platform/ff420000.dwmmc/by-name/system", O_RDONLY) = 3
ioctl(3, BLKROSET, 0)  = -1 EPERM (Operation not permitted)

Fixes: a5f5774c55a2 ("mmc: block: Add new ioctl to send multi commands")
Cc: stable@vger.kernel.org
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 47bc87d..3bdbe50 100644 (file)
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -589,6 +589,14 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
        struct mmc_card *card;
        int err = 0, ioc_err = 0;
 
+       /*
+        * The caller must have CAP_SYS_RAWIO, and must be calling this on the
+        * whole block device, not on a partition.  This prevents overspray
+        * between sibling partitions.
+        */
+       if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
+               return -EPERM;
+
        idata = mmc_blk_ioctl_copy_from_user(ic_ptr);
        if (IS_ERR(idata))
                return PTR_ERR(idata);
@@ -631,6 +639,14 @@ static int mmc_blk_ioctl_multi_cmd(struct block_device *bdev,
        int i, err = 0, ioc_err = 0;
        __u64 num_of_cmds;
 
+       /*
+        * The caller must have CAP_SYS_RAWIO, and must be calling this on the
+        * whole block device, not on a partition.  This prevents overspray
+        * between sibling partitions.
+        */
+       if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
+               return -EPERM;
+
        if (copy_from_user(&num_of_cmds, &user->num_of_cmds,
                           sizeof(num_of_cmds)))
                return -EFAULT;
@@ -688,14 +704,6 @@ cmd_err:
 static int mmc_blk_ioctl(struct block_device *bdev, fmode_t mode,
        unsigned int cmd, unsigned long arg)
 {
-       /*
-        * The caller must have CAP_SYS_RAWIO, and must be calling this on the
-        * whole block device, not on a partition.  This prevents overspray
-        * between sibling partitions.
-        */
-       if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
-               return -EPERM;
-
        switch (cmd) {
        case MMC_IOC_CMD:
                return mmc_blk_ioctl_cmd(bdev,