The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x 8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025101635-unbuckled-masses-9441@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o tytso@mit.edu Date: Tue, 16 Sep 2025 23:22:47 -0400 Subject: [PATCH] ext4: avoid potential buffer over-read in parse_apply_sb_mount_options()

Unlike other strings in the ext4 superblock, we rely on tune2fs to make sure s_mount_opts is NUL terminated. Harden parse_apply_sb_mount_options() by treating s_mount_opts as a potential __nonstring.

Cc: stable@vger.kernel.org Fixes: 8b67f04ab9de ("ext4: Add mount options in superblock") Reviewed-by: Jan Kara jack@suse.cz Reviewed-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Theodore Ts'o tytso@mit.edu Message-ID: 20250916-tune2fs-v2-1-d594dc7486f0@mit.edu Signed-off-by: Theodore Ts'o tytso@mit.edu

diff --git a/fs/ext4/super.c b/fs/ext4/super.c index d26e5c0731e5..488f4c281a3f 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2469,7 +2469,7 @@ static int parse_apply_sb_mount_options(struct super_block *sb, struct ext4_fs_context *m_ctx) { struct ext4_sb_info *sbi = EXT4_SB(sb); - char *s_mount_opts = NULL; + char s_mount_opts[65]; struct ext4_fs_context *s_ctx = NULL; struct fs_context *fc = NULL; int ret = -ENOMEM; @@ -2477,15 +2477,11 @@ static int parse_apply_sb_mount_options(struct super_block *sb, if (!sbi->s_es->s_mount_opts[0]) return 0;

- s_mount_opts = kstrndup(sbi->s_es->s_mount_opts, - sizeof(sbi->s_es->s_mount_opts), - GFP_KERNEL); - if (!s_mount_opts) - return ret; + strscpy_pad(s_mount_opts, sbi->s_es->s_mount_opts);

fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL); if (!fc) - goto out_free; + return -ENOMEM;

s_ctx = kzalloc(sizeof(struct ext4_fs_context), GFP_KERNEL); if (!s_ctx) @@ -2517,11 +2513,8 @@ static int parse_apply_sb_mount_options(struct super_block *sb, ret = 0;

out_free: - if (fc) { - ext4_fc_free(fc); - kfree(fc); - } - kfree(s_mount_opts); + ext4_fc_free(fc); + kfree(fc); return ret; }