From 2a0cf438320cdb783e0378570744c0ef0d83e934 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Tue, 16 Sep 2025 23:22:47 -0400 Subject: [PATCH] ext4: avoid potential buffer over-read in parse_apply_sb_mount_options() commit 8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8 upstream. 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 Reviewed-by: Darrick J. Wong Signed-off-by: Theodore Ts'o Message-ID: <20250916-tune2fs-v2-1-d594dc7486f0@mit.edu> Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- fs/ext4/super.c | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index b7a2eebcc2941..78ecdedadb076 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2493,7 +2493,7 @@ 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; @@ -2501,15 +2501,11 @@ 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) @@ -2541,11 +2537,8 @@ parse_failed: ret = 0; out_free: - if (fc) { - ext4_fc_free(fc); - kfree(fc); - } - kfree(s_mount_opts); + ext4_fc_free(fc); + kfree(fc); return ret; } -- 2.47.3