linux-ext4 - [RESEND PATCH v2 2/5] ext4: fsmap: Check fmh_iflags value directly on the user copied data

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Message-ID: <20230508154230.159654-3-tudor.ambarus@linaro.org>
Date:   Mon,  8 May 2023 15:42:27 +0000
From:   Tudor Ambarus <tudor.ambarus@...aro.org>
To:     tytso@....edu
Cc:     adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, joneslee@...gle.com,
        Tudor Ambarus <tudor.ambarus@...aro.org>
Subject: [RESEND PATCH v2 2/5] ext4: fsmap: Check fmh_iflags value directly on the user copied data

struct ext4_fsmap_head is the ext4 internal fsmap representation of
struct fsmap_head. As the code was, the fmh_iflags validation was done
on the fmh_iflags value of the internal fsmap representation. Since
xhead.fmh_iflags is initialized with head.fmh_iflags and not changed
afterwards, do the validation of fmh_iflags directly on fsmap_head data,
it spares some superfluous initializations in case the user provides a
wrong value for fmh_iflags.

Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
---
 fs/ext4/fsmap.c | 2 --
 fs/ext4/ioctl.c | 2 ++
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/fsmap.c b/fs/ext4/fsmap.c
index cdf9bfe10137..7765293bfa5d 100644
--- a/fs/ext4/fsmap.c
+++ b/fs/ext4/fsmap.c
@@ -635,8 +635,6 @@ int ext4_getfsmap(struct super_block *sb, struct ext4_fsmap_head *head,
 	int i;
 	int error = 0;
 
-	if (head->fmh_iflags & ~FMH_IF_VALID)
-		return -EINVAL;
 	if (!ext4_getfsmap_is_valid_device(sb, &head->fmh_keys[0]) ||
 	    !ext4_getfsmap_is_valid_device(sb, &head->fmh_keys[1]))
 		return -EINVAL;
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 6d5210b94ac2..a585d96567b5 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -873,6 +873,8 @@ static int ext4_ioc_getfsmap(struct super_block *sb,
 
 	if (copy_from_user(&head, arg, sizeof(struct fsmap_head)))
 		return -EFAULT;
+	if (head.fmh_iflags & ~FMH_IF_VALID)
+		return -EINVAL;
 	if (memchr_inv(head.fmh_reserved, 0, sizeof(head.fmh_reserved)) ||
 	    memchr_inv(head.fmh_keys[0].fmr_reserved, 0,
 		       sizeof(head.fmh_keys[0].fmr_reserved)) ||
-- 
2.40.1.521.gf1e218fcd8-goog