* [PATCH] tune2fs: prohibit toggling uninit_bg on live filesystems
@ 2019-11-20 19:32 Darrick J. Wong
2019-11-21 18:22 ` Theodore Y. Ts'o
0 siblings, 1 reply; 2+ messages in thread
From: Darrick J. Wong @ 2019-11-20 19:32 UTC (permalink / raw)
To: Theodore Ts'o; +Cc: linux-ext4, eric.saint.etienne
From: Darrick J. Wong <darrick.wong@oracle.com>
An internal customer followed an erroneous AskUbuntu article[1] to try to
change the UUID of a live ext4 filesystem. The article claims that you
can work around tune2fs' "cannot change UUID on live fs" error by
disabling uninit_bg, changing the UUID, and re-enabling the feature.
This led to metadata corruption because tune2fs' journal descriptor
rewrite races with regular filesystem writes. Therefore, prevent
administrators from turning on or off uninit_bg on a mounted fs.
[1] https://askubuntu.com/questions/132079/how-do-i-change-uuid-of-a-disk-to-whatever-i-want/195839#459097
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
misc/tune2fs.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/misc/tune2fs.c b/misc/tune2fs.c
index 8368a733..150dc916 100644
--- a/misc/tune2fs.c
+++ b/misc/tune2fs.c
@@ -1312,6 +1312,12 @@ static int update_feature_set(ext2_filsys fs, char *features)
if (FEATURE_ON(E2P_FEATURE_RO_INCOMPAT,
EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
+ if (mount_flags & EXT2_MF_MOUNTED) {
+ fputs(_("Cannot enable uninit_bg on a mounted "
+ "filesystem!\n"), stderr);
+ exit(1);
+ }
+
/* Do not enable uninit_bg when metadata_csum enabled */
if (ext2fs_has_feature_metadata_csum(fs->super))
ext2fs_clear_feature_gdt_csum(fs->super);
@@ -1321,6 +1327,12 @@ static int update_feature_set(ext2_filsys fs, char *features)
if (FEATURE_OFF(E2P_FEATURE_RO_INCOMPAT,
EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
+ if (mount_flags & EXT2_MF_MOUNTED) {
+ fputs(_("Cannot disable uninit_bg on a mounted "
+ "filesystem!\n"), stderr);
+ exit(1);
+ }
+
err = disable_uninit_bg(fs,
EXT4_FEATURE_RO_COMPAT_GDT_CSUM);
if (err)
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] tune2fs: prohibit toggling uninit_bg on live filesystems
2019-11-20 19:32 [PATCH] tune2fs: prohibit toggling uninit_bg on live filesystems Darrick J. Wong
@ 2019-11-21 18:22 ` Theodore Y. Ts'o
0 siblings, 0 replies; 2+ messages in thread
From: Theodore Y. Ts'o @ 2019-11-21 18:22 UTC (permalink / raw)
To: Darrick J. Wong; +Cc: linux-ext4, eric.saint.etienne
On Wed, Nov 20, 2019 at 11:32:55AM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> An internal customer followed an erroneous AskUbuntu article[1] to try to
> change the UUID of a live ext4 filesystem. The article claims that you
> can work around tune2fs' "cannot change UUID on live fs" error by
> disabling uninit_bg, changing the UUID, and re-enabling the feature.
>
> This led to metadata corruption because tune2fs' journal descriptor
> rewrite races with regular filesystem writes. Therefore, prevent
> administrators from turning on or off uninit_bg on a mounted fs.
>
> [1] https://askubuntu.com/questions/132079/how-do-i-change-uuid-of-a-disk-to-whatever-i-want/195839#459097
>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Thanks, applied.
- Ted
^ permalink raw reply [flat|nested] 2+ messages in thread
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2019-11-21 18:22 ` Theodore Y. Ts'o
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