[PATCH v2 0/3] ext4: Add support for mounted updates to the superblock via an ioctl

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Gratulujeme, nabidka daru

Backport request for commit...

Theodore Ts'o via B4 Relay

17 Sep 2025 17 Sep '25

3:22 a.m.

This patch series enables a future version of tune2fs to be able to modify certain parts of the ext4 superblock without to write to the block device.

The first patch fixes a potential buffer overrun caused by a maliciously moified superblock. The second patch adds support for 32-bit uid and gid's which can have access to the reserved blocks pool. The last patch adds the ioctl's which will be used by tune2fs.

Signed-off-by: Theodore Ts'o tytso@mit.edu --- Changes in v2: - fix bugs that were detected using sparse - remove tune (unsafe) ability to clear certain compat faatures - add the ability to set the encoding and encoding flags for case folding - Link to v1: https://lore.kernel.org/r/20250908-tune2fs-v1-0-e3a6929f3355@mit.edu

--- Theodore Ts'o (3): ext4: avoid potential buffer over-read in parse_apply_sb_mount_options() ext4: add support for 32-bit default reserved uid and gid values ext4: implemet new ioctls to set and get superblock parameters

fs/ext4/ext4.h | 16 +++- fs/ext4/ioctl.c | 312 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-- fs/ext4/super.c | 25 +++---- include/uapi/linux/ext4.h | 53 +++++++++++++ 4 files changed, 382 insertions(+), 24 deletions(-) --- base-commit: b320789d6883cc00ac78ce83bccbfe7ed58afcf0 change-id: 20250830-tune2fs-3376beb72403

Best regards,

-- Theodore Ts'o tytso@mit.edu

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Theodore Ts'o via B4 Relay

17 Sep 17 Sep

3:22 a.m.

New subject: [PATCH v2 1/3] ext4: avoid potential buffer over-read in parse_apply_sb_mount_options()

From: Theodore Ts'o tytso@mit.edu

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") Signed-off-by: Theodore Ts'o tytso@mit.edu --- 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 699c15db28a82f26809bf68533454a242596f0fd..94c98446c84f9a4614971d246ca7f001de610a8a 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2460,7 +2460,7 @@ 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; @@ -2468,15 +2468,11 @@ 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) @@ -2508,11 +2504,8 @@ 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; }

-- 2.51.0

Jan Kara

4:05 p.m.

New subject: [PATCH v2 1/3] ext4: avoid potential buffer over-read in parse_apply_sb_mount_options()

On Tue 16-09-25 23:22:47, Theodore Ts'o via B4 Relay wrote:

...

From: Theodore Ts'o tytso@mit.edu

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") Signed-off-by: Theodore Ts'o tytso@mit.edu

Looks good. Feel free to add:

Reviewed-by: Jan Kara jack@suse.cz

Honza

...

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 699c15db28a82f26809bf68533454a242596f0fd..94c98446c84f9a4614971d246ca7f001de610a8a 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2460,7 +2460,7 @@ 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;

@@ -2468,15 +2468,11 @@ 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) @@ -2508,11 +2504,8 @@ 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;

}

-- 2.51.0

-- Jan Kara jack@suse.com SUSE Labs, CR

Darrick J. Wong

18 Sep 18 Sep

4:55 p.m.

New subject: [PATCH v2 1/3] ext4: avoid potential buffer over-read in parse_apply_sb_mount_options()

On Wed, Sep 17, 2025 at 06:05:06PM +0200, Jan Kara wrote:

...

On Tue 16-09-25 23:22:47, Theodore Ts'o via B4 Relay wrote:

...
From: Theodore Ts'o tytso@mit.edu

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") Signed-off-by: Theodore Ts'o tytso@mit.edu

Looks good. Feel free to add:

Reviewed-by: Jan Kara jack@suse.cz

Looks fine to me too, Reviewed-by: "Darrick J. Wong" djwong@kernel.org

--D

...

						Honza
...
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 699c15db28a82f26809bf68533454a242596f0fd..94c98446c84f9a4614971d246ca7f001de610a8a 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2460,7 +2460,7 @@ 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;

@@ -2468,15 +2468,11 @@ 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) @@ -2508,11 +2504,8 @@ 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;

}

-- 2.51.0
-- Jan Kara jack@suse.com SUSE Labs, CR

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Darrick J. Wong
Jan Kara
Theodore Ts'o via B4 Relay