[PATCH] [v2] block: fix FS_IOC_GETLBMD_CAP parsing in blkdev_common_ioctl()

[Arnd Bergmann <arnd@kernel.org>]

From: Arnd Bergmann <arnd@arndb.de>

Anders and Naresh found that the addition of the FS_IOC_GETLBMD_CAP
handling in the blockdev ioctl handler breaks all ioctls with
_IOC_NR==2, as the new command is not added to the switch but only
a few of the command bits are check.

Move the check into the blk_get_meta_cap() function itself and make
it return -ENOIOCTLCMD for any unsupported command code, including
those with a smaller size that previously returned -EINVAL.

For consistency this also drops the check for NULL 'arg' that
is really useless, as any invalid pointer should return -EFAULT.

Fixes: 9eb22f7fedfc ("fs: add ioctl to query metadata and protection info capabilities")
Link: https://lore.kernel.org/all/CA+G9fYvk9HHE5UJ7cdJHTcY6P5JKnp+_e+sdC5U-ZQFTP9_hqQ@mail.gmail.com/
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Anders Roxell <anders.roxell@linaro.org>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
v2: add the check in blk-integrity.c instead of ioctl.c

I've left out the maximum-size check this time, as there was no
consensus on whether there should be one, or what value.

We still need to come up with a better way of handling these in
general, for now the patch just addresses the immediate regression
that Naresh found.

I have also sent a handful of patches for other drivers that have
variations of the same bug.
---
 block/blk-integrity.c | 10 ++++++----
 block/ioctl.c         |  6 ++++--
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/block/blk-integrity.c b/block/blk-integrity.c
index 9d9dc9c32083..61a79e19c78f 100644
--- a/block/blk-integrity.c
+++ b/block/blk-integrity.c
@@ -62,10 +62,12 @@ int blk_get_meta_cap(struct block_device *bdev, unsigned int cmd,
 	struct logical_block_metadata_cap meta_cap = {};
 	size_t usize = _IOC_SIZE(cmd);
 
-	if (!argp)
-		return -EINVAL;
-	if (usize < LBMD_SIZE_VER0)
-		return -EINVAL;
+	if (_IOC_DIR(cmd)  != _IOC_DIR(FS_IOC_GETLBMD_CAP) ||
+	    _IOC_TYPE(cmd) != _IOC_TYPE(FS_IOC_GETLBMD_CAP) ||
+	    _IOC_NR(cmd)   != _IOC_NR(FS_IOC_GETLBMD_CAP) ||
+	    _IOC_SIZE(cmd) < LBMD_SIZE_VER0)
+		return -ENOIOCTLCMD;
+
 	if (!bi)
 		goto out;
 
diff --git a/block/ioctl.c b/block/ioctl.c
index 9ad403733e19..af2e22e5533c 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -566,9 +566,11 @@ static int blkdev_common_ioctl(struct block_device *bdev, blk_mode_t mode,
 			       void __user *argp)
 {
 	unsigned int max_sectors;
+	int ret;
 
-	if (_IOC_NR(cmd) == _IOC_NR(FS_IOC_GETLBMD_CAP))
-		return blk_get_meta_cap(bdev, cmd, argp);
+	ret = blk_get_meta_cap(bdev, cmd, argp);
+	if (ret != -ENOIOCTLCMD)
+		return ret;
 
 	switch (cmd) {
 	case BLKFLSBUF:
-- 
2.39.5