* [PATCH v2 2/2] ext4: check if mount_opts is NUL-terminated in ext4_ioctl_set_tune_sb()
2025-11-01 16:04 [PATCH v2 1/2] ext4: fix string copying in parse_apply_sb_mount_options() Fedor Pchelkin
@ 2025-11-01 16:04 ` Fedor Pchelkin
2025-11-03 11:39 ` Jan Kara
2025-11-08 4:05 ` Baokun Li
2025-11-03 11:38 ` [PATCH v2 1/2] ext4: fix string copying in parse_apply_sb_mount_options() Jan Kara
` (2 subsequent siblings)
3 siblings, 2 replies; 7+ messages in thread
From: Fedor Pchelkin @ 2025-11-01 16:04 UTC (permalink / raw)
To: Theodore Ts'o, Jan Kara, linux-ext4
Cc: Fedor Pchelkin, Andreas Dilger, Darrick J. Wong, linux-kernel,
lvc-project
params.mount_opts may come as potentially non-NUL-term string. Userspace
is expected to pass a NUL-term string. Add an extra check to ensure this
holds true. Note that further code utilizes strscpy_pad() so this is just
for proper informing the user of incorrect data being provided.
Found by Linux Verification Center (linuxtesting.org).
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
---
v2: check length of mount_opts in superblock tuning ioctl (Jan Kara)
Can't plainly return error at strscpy_pad() call site in
ext4_sb_setparams(), that's a void ext4_update_sb_callback.
v1: https://lore.kernel.org/lkml/20251028130949.599847-1-pchelkin@ispras.ru/T/#u
fs/ext4/ioctl.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index a93a7baae990..3dec26c939fd 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -1394,6 +1394,10 @@ static int ext4_ioctl_set_tune_sb(struct file *filp,
if (copy_from_user(¶ms, in, sizeof(params)))
return -EFAULT;
+ if (strnlen(params.mount_opts, sizeof(params.mount_opts)) ==
+ sizeof(params.mount_opts))
+ return -E2BIG;
+
if ((params.set_flags & ~TUNE_OPS_SUPPORTED) != 0)
return -EOPNOTSUPP;
--
2.51.0
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH v2 2/2] ext4: check if mount_opts is NUL-terminated in ext4_ioctl_set_tune_sb()
2025-11-01 16:04 ` [PATCH v2 2/2] ext4: check if mount_opts is NUL-terminated in ext4_ioctl_set_tune_sb() Fedor Pchelkin
@ 2025-11-03 11:39 ` Jan Kara
2025-11-08 4:05 ` Baokun Li
1 sibling, 0 replies; 7+ messages in thread
From: Jan Kara @ 2025-11-03 11:39 UTC (permalink / raw)
To: Fedor Pchelkin
Cc: Theodore Ts'o, Jan Kara, linux-ext4, Andreas Dilger,
Darrick J. Wong, linux-kernel, lvc-project
On Sat 01-11-25 19:04:29, Fedor Pchelkin wrote:
> params.mount_opts may come as potentially non-NUL-term string. Userspace
> is expected to pass a NUL-term string. Add an extra check to ensure this
> holds true. Note that further code utilizes strscpy_pad() so this is just
> for proper informing the user of incorrect data being provided.
>
> Found by Linux Verification Center (linuxtesting.org).
>
> Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@suse.cz>
Honza
> ---
>
> v2: check length of mount_opts in superblock tuning ioctl (Jan Kara)
>
> Can't plainly return error at strscpy_pad() call site in
> ext4_sb_setparams(), that's a void ext4_update_sb_callback.
>
> v1: https://lore.kernel.org/lkml/20251028130949.599847-1-pchelkin@ispras.ru/T/#u
>
> fs/ext4/ioctl.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
> index a93a7baae990..3dec26c939fd 100644
> --- a/fs/ext4/ioctl.c
> +++ b/fs/ext4/ioctl.c
> @@ -1394,6 +1394,10 @@ static int ext4_ioctl_set_tune_sb(struct file *filp,
> if (copy_from_user(¶ms, in, sizeof(params)))
> return -EFAULT;
>
> + if (strnlen(params.mount_opts, sizeof(params.mount_opts)) ==
> + sizeof(params.mount_opts))
> + return -E2BIG;
> +
> if ((params.set_flags & ~TUNE_OPS_SUPPORTED) != 0)
> return -EOPNOTSUPP;
>
> --
> 2.51.0
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2 2/2] ext4: check if mount_opts is NUL-terminated in ext4_ioctl_set_tune_sb()
2025-11-01 16:04 ` [PATCH v2 2/2] ext4: check if mount_opts is NUL-terminated in ext4_ioctl_set_tune_sb() Fedor Pchelkin
2025-11-03 11:39 ` Jan Kara
@ 2025-11-08 4:05 ` Baokun Li
1 sibling, 0 replies; 7+ messages in thread
From: Baokun Li @ 2025-11-08 4:05 UTC (permalink / raw)
To: Fedor Pchelkin
Cc: Theodore Ts'o, linux-ext4, Jan Kara, Andreas Dilger,
Darrick J. Wong, linux-kernel, lvc-project
On 2025-11-02 00:04, Fedor Pchelkin wrote:
> params.mount_opts may come as potentially non-NUL-term string. Userspace
> is expected to pass a NUL-term string. Add an extra check to ensure this
> holds true. Note that further code utilizes strscpy_pad() so this is just
> for proper informing the user of incorrect data being provided.
>
> Found by Linux Verification Center (linuxtesting.org).
>
> Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Looks good to me.
Reviewed-by: Baokun Li <libaokun1@huawei.com>
> ---
>
> v2: check length of mount_opts in superblock tuning ioctl (Jan Kara)
>
> Can't plainly return error at strscpy_pad() call site in
> ext4_sb_setparams(), that's a void ext4_update_sb_callback.
>
> v1: https://lore.kernel.org/lkml/20251028130949.599847-1-pchelkin@ispras.ru/T/#u
>
> fs/ext4/ioctl.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
> index a93a7baae990..3dec26c939fd 100644
> --- a/fs/ext4/ioctl.c
> +++ b/fs/ext4/ioctl.c
> @@ -1394,6 +1394,10 @@ static int ext4_ioctl_set_tune_sb(struct file *filp,
> if (copy_from_user(¶ms, in, sizeof(params)))
> return -EFAULT;
>
> + if (strnlen(params.mount_opts, sizeof(params.mount_opts)) ==
> + sizeof(params.mount_opts))
> + return -E2BIG;
> +
> if ((params.set_flags & ~TUNE_OPS_SUPPORTED) != 0)
> return -EOPNOTSUPP;
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v2 1/2] ext4: fix string copying in parse_apply_sb_mount_options()
2025-11-01 16:04 [PATCH v2 1/2] ext4: fix string copying in parse_apply_sb_mount_options() Fedor Pchelkin
2025-11-01 16:04 ` [PATCH v2 2/2] ext4: check if mount_opts is NUL-terminated in ext4_ioctl_set_tune_sb() Fedor Pchelkin
@ 2025-11-03 11:38 ` Jan Kara
2025-11-08 4:04 ` Baokun Li
2025-11-17 19:13 ` Theodore Ts'o
3 siblings, 0 replies; 7+ messages in thread
From: Jan Kara @ 2025-11-03 11:38 UTC (permalink / raw)
To: Fedor Pchelkin
Cc: Theodore Ts'o, Jan Kara, linux-ext4, Andreas Dilger,
Darrick J. Wong, linux-kernel, lvc-project, stable
On Sat 01-11-25 19:04:28, Fedor Pchelkin wrote:
> strscpy_pad() can't be used to copy a non-NUL-term string into a NUL-term
> string of possibly bigger size. Commit 0efc5990bca5 ("string.h: Introduce
> memtostr() and memtostr_pad()") provides additional information in that
> regard. So if this happens, the following warning is observed:
>
> strnlen: detected buffer overflow: 65 byte read of buffer size 64
> WARNING: CPU: 0 PID: 28655 at lib/string_helpers.c:1032 __fortify_report+0x96/0xc0 lib/string_helpers.c:1032
> Modules linked in:
> CPU: 0 UID: 0 PID: 28655 Comm: syz-executor.3 Not tainted 6.12.54-syzkaller-00144-g5f0270f1ba00 #0
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> RIP: 0010:__fortify_report+0x96/0xc0 lib/string_helpers.c:1032
> Call Trace:
> <TASK>
> __fortify_panic+0x1f/0x30 lib/string_helpers.c:1039
> strnlen include/linux/fortify-string.h:235 [inline]
> sized_strscpy include/linux/fortify-string.h:309 [inline]
> parse_apply_sb_mount_options fs/ext4/super.c:2504 [inline]
> __ext4_fill_super fs/ext4/super.c:5261 [inline]
> ext4_fill_super+0x3c35/0xad00 fs/ext4/super.c:5706
> get_tree_bdev_flags+0x387/0x620 fs/super.c:1636
> vfs_get_tree+0x93/0x380 fs/super.c:1814
> do_new_mount fs/namespace.c:3553 [inline]
> path_mount+0x6ae/0x1f70 fs/namespace.c:3880
> do_mount fs/namespace.c:3893 [inline]
> __do_sys_mount fs/namespace.c:4103 [inline]
> __se_sys_mount fs/namespace.c:4080 [inline]
> __x64_sys_mount+0x280/0x300 fs/namespace.c:4080
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0x64/0x140 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
> Since userspace is expected to provide s_mount_opts field to be at most 63
> characters long with the ending byte being NUL-term, use a 64-byte buffer
> which matches the size of s_mount_opts, so that strscpy_pad() does its job
> properly. Return with error if the user still managed to provide a
> non-NUL-term string here.
>
> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
>
> Fixes: 8ecb790ea8c3 ("ext4: avoid potential buffer over-read in parse_apply_sb_mount_options()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@suse.cz>
Honza
> ---
>
> v2: - treat non-NUL-term s_mount_opts as invalid case (Jan Kara)
> - swap order of patches in series so the fixing-one goes first
>
> v1: https://lore.kernel.org/lkml/20251028130949.599847-1-pchelkin@ispras.ru/T/#u
>
> fs/ext4/super.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 33e7c08c9529..15bef41f08bd 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -2475,7 +2475,7 @@ 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[65];
> + char s_mount_opts[64];
> struct ext4_fs_context *s_ctx = NULL;
> struct fs_context *fc = NULL;
> int ret = -ENOMEM;
> @@ -2483,7 +2483,8 @@ static int parse_apply_sb_mount_options(struct super_block *sb,
> if (!sbi->s_es->s_mount_opts[0])
> return 0;
>
> - strscpy_pad(s_mount_opts, sbi->s_es->s_mount_opts);
> + if (strscpy_pad(s_mount_opts, sbi->s_es->s_mount_opts) < 0)
> + return -E2BIG;
>
> fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL);
> if (!fc)
> --
> 2.51.0
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH v2 1/2] ext4: fix string copying in parse_apply_sb_mount_options()
2025-11-01 16:04 [PATCH v2 1/2] ext4: fix string copying in parse_apply_sb_mount_options() Fedor Pchelkin
2025-11-01 16:04 ` [PATCH v2 2/2] ext4: check if mount_opts is NUL-terminated in ext4_ioctl_set_tune_sb() Fedor Pchelkin
2025-11-03 11:38 ` [PATCH v2 1/2] ext4: fix string copying in parse_apply_sb_mount_options() Jan Kara
@ 2025-11-08 4:04 ` Baokun Li
2025-11-17 19:13 ` Theodore Ts'o
3 siblings, 0 replies; 7+ messages in thread
From: Baokun Li @ 2025-11-08 4:04 UTC (permalink / raw)
To: Fedor Pchelkin
Cc: Theodore Ts'o, Jan Kara, linux-ext4, Andreas Dilger,
Darrick J. Wong, linux-kernel, lvc-project, stable
On 2025-11-02 00:04, Fedor Pchelkin wrote:
> strscpy_pad() can't be used to copy a non-NUL-term string into a NUL-term
> string of possibly bigger size. Commit 0efc5990bca5 ("string.h: Introduce
> memtostr() and memtostr_pad()") provides additional information in that
> regard. So if this happens, the following warning is observed:
>
> strnlen: detected buffer overflow: 65 byte read of buffer size 64
> WARNING: CPU: 0 PID: 28655 at lib/string_helpers.c:1032 __fortify_report+0x96/0xc0 lib/string_helpers.c:1032
> Modules linked in:
> CPU: 0 UID: 0 PID: 28655 Comm: syz-executor.3 Not tainted 6.12.54-syzkaller-00144-g5f0270f1ba00 #0
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> RIP: 0010:__fortify_report+0x96/0xc0 lib/string_helpers.c:1032
> Call Trace:
> <TASK>
> __fortify_panic+0x1f/0x30 lib/string_helpers.c:1039
> strnlen include/linux/fortify-string.h:235 [inline]
> sized_strscpy include/linux/fortify-string.h:309 [inline]
> parse_apply_sb_mount_options fs/ext4/super.c:2504 [inline]
> __ext4_fill_super fs/ext4/super.c:5261 [inline]
> ext4_fill_super+0x3c35/0xad00 fs/ext4/super.c:5706
> get_tree_bdev_flags+0x387/0x620 fs/super.c:1636
> vfs_get_tree+0x93/0x380 fs/super.c:1814
> do_new_mount fs/namespace.c:3553 [inline]
> path_mount+0x6ae/0x1f70 fs/namespace.c:3880
> do_mount fs/namespace.c:3893 [inline]
> __do_sys_mount fs/namespace.c:4103 [inline]
> __se_sys_mount fs/namespace.c:4080 [inline]
> __x64_sys_mount+0x280/0x300 fs/namespace.c:4080
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0x64/0x140 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
> Since userspace is expected to provide s_mount_opts field to be at most 63
> characters long with the ending byte being NUL-term, use a 64-byte buffer
> which matches the size of s_mount_opts, so that strscpy_pad() does its job
> properly. Return with error if the user still managed to provide a
> non-NUL-term string here.
>
> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
>
> Fixes: 8ecb790ea8c3 ("ext4: avoid potential buffer over-read in parse_apply_sb_mount_options()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Looks good to me.
Reviewed-by: Baokun Li <libaokun1@huawei.com>
> ---
>
> v2: - treat non-NUL-term s_mount_opts as invalid case (Jan Kara)
> - swap order of patches in series so the fixing-one goes first
>
> v1: https://lore.kernel.org/lkml/20251028130949.599847-1-pchelkin@ispras.ru/T/#u
>
> fs/ext4/super.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 33e7c08c9529..15bef41f08bd 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -2475,7 +2475,7 @@ 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[65];
> + char s_mount_opts[64];
> struct ext4_fs_context *s_ctx = NULL;
> struct fs_context *fc = NULL;
> int ret = -ENOMEM;
> @@ -2483,7 +2483,8 @@ static int parse_apply_sb_mount_options(struct super_block *sb,
> if (!sbi->s_es->s_mount_opts[0])
> return 0;
>
> - strscpy_pad(s_mount_opts, sbi->s_es->s_mount_opts);
> + if (strscpy_pad(s_mount_opts, sbi->s_es->s_mount_opts) < 0)
> + return -E2BIG;
>
> fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL);
> if (!fc)
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH v2 1/2] ext4: fix string copying in parse_apply_sb_mount_options()
2025-11-01 16:04 [PATCH v2 1/2] ext4: fix string copying in parse_apply_sb_mount_options() Fedor Pchelkin
` (2 preceding siblings ...)
2025-11-08 4:04 ` Baokun Li
@ 2025-11-17 19:13 ` Theodore Ts'o
3 siblings, 0 replies; 7+ messages in thread
From: Theodore Ts'o @ 2025-11-17 19:13 UTC (permalink / raw)
To: Jan Kara, linux-ext4, Fedor Pchelkin
Cc: Theodore Ts'o, Andreas Dilger, Darrick J. Wong, linux-kernel,
lvc-project, stable
On Sat, 01 Nov 2025 19:04:28 +0300, Fedor Pchelkin wrote:
> strscpy_pad() can't be used to copy a non-NUL-term string into a NUL-term
> string of possibly bigger size. Commit 0efc5990bca5 ("string.h: Introduce
> memtostr() and memtostr_pad()") provides additional information in that
> regard. So if this happens, the following warning is observed:
>
> strnlen: detected buffer overflow: 65 byte read of buffer size 64
> WARNING: CPU: 0 PID: 28655 at lib/string_helpers.c:1032 __fortify_report+0x96/0xc0 lib/string_helpers.c:1032
> Modules linked in:
> CPU: 0 UID: 0 PID: 28655 Comm: syz-executor.3 Not tainted 6.12.54-syzkaller-00144-g5f0270f1ba00 #0
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> RIP: 0010:__fortify_report+0x96/0xc0 lib/string_helpers.c:1032
> Call Trace:
> <TASK>
> __fortify_panic+0x1f/0x30 lib/string_helpers.c:1039
> strnlen include/linux/fortify-string.h:235 [inline]
> sized_strscpy include/linux/fortify-string.h:309 [inline]
> parse_apply_sb_mount_options fs/ext4/super.c:2504 [inline]
> __ext4_fill_super fs/ext4/super.c:5261 [inline]
> ext4_fill_super+0x3c35/0xad00 fs/ext4/super.c:5706
> get_tree_bdev_flags+0x387/0x620 fs/super.c:1636
> vfs_get_tree+0x93/0x380 fs/super.c:1814
> do_new_mount fs/namespace.c:3553 [inline]
> path_mount+0x6ae/0x1f70 fs/namespace.c:3880
> do_mount fs/namespace.c:3893 [inline]
> __do_sys_mount fs/namespace.c:4103 [inline]
> __se_sys_mount fs/namespace.c:4080 [inline]
> __x64_sys_mount+0x280/0x300 fs/namespace.c:4080
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0x64/0x140 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
> [...]
Applied, thanks!
[1/2] ext4: fix string copying in parse_apply_sb_mount_options()
commit: c517b381de9490b910ab451c2177aa32064678ad
[2/2] ext4: check if mount_opts is NUL-terminated in ext4_ioctl_set_tune_sb()
commit: 687524bafd4e86cfa783857f8045460f4caee921
Best regards,
--
Theodore Ts'o <tytso@mit.edu>
^ permalink raw reply [flat|nested] 7+ messages in thread