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ext4: improve error recovery code paths in __ext4_remount() 

If there are failures while changing the mount options in
__ext4_remount(), we need to restore the old mount options.

This commit fixes two problem.  The first is there is a chance that we
will free the old quota file names before a potential failure leading
to a use-after-free.  The second problem addressed in this commit is
if there is a failed read/write to read-only transition, if the quota
has already been suspended, we need to renable quota handling.

Cc: stable@kernel.org
Link: https://lore.kernel.org/r/20230506142419.984260-2-tytso@mit.edu
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2023-05-05 22:20:29 -04:00
parent 4b3cb1d108
commit 4c0b4818b1
1 changed files with 10 additions and 3 deletions
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13
fs/ext4/super.c
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@ -6617,9 +6617,6 @@ static int __ext4_remount(struct fs_context *fc, struct super_block *sb)
}
#ifdef CONFIG_QUOTA
/* Release old quota file names */
for (i = 0; i < EXT4_MAXQUOTAS; i++)
kfree(old_opts.s_qf_names[i]);
if (enable_quota) {
if (sb_any_quota_suspended(sb))
dquot_resume(sb, -1);
@ -6629,6 +6626,9 @@ static int __ext4_remount(struct fs_context *fc, struct super_block *sb)
goto restore_opts;
}
}
/* Release old quota file names */
for (i = 0; i < EXT4_MAXQUOTAS; i++)
kfree(old_opts.s_qf_names[i]);
#endif
if (!test_opt(sb, BLOCK_VALIDITY) && sbi->s_system_blks)
ext4_release_system_zone(sb);
@ -6642,6 +6642,13 @@ static int __ext4_remount(struct fs_context *fc, struct super_block *sb)
return 0;
restore_opts:
/*
* If there was a failing r/w to ro transition, we may need to
* re-enable quota
*/
if ((sb->s_flags & SB_RDONLY) && !(old_sb_flags & SB_RDONLY) &&
sb_any_quota_suspended(sb))
dquot_resume(sb, -1);
sb->s_flags = old_sb_flags;
sbi->s_mount_opt = old_opts.s_mount_opt;
sbi->s_mount_opt2 = old_opts.s_mount_opt2;