diff options
| author | Theodore Ts'o <tytso@mit.edu> | 2020-06-10 11:16:37 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-06-24 17:50:48 +0200 |
| commit | ffa9206a62d3894d2a8580bf106db55a85cfb013 (patch) | |
| tree | e71988cd3c3316f8e6f8be7487829e494cbff5c1 | |
| parent | 0804b23d2ff15f6656d70291d5e07677ca897881 (diff) | |
ext4: avoid race conditions when remounting with options that change dax
[ Upstream commit 829b37b8cddb1db75c1b7905505b90e593b15db1 ]
Trying to change dax mount options when remounting could allow mount
options to be enabled for a small amount of time, and then the mount
option change would be reverted.
In the case of "mount -o remount,dax", this can cause a race where
files would temporarily treated as DAX --- and then not.
Cc: stable@kernel.org
Reported-by: syzbot+bca9799bf129256190da@syzkaller.appspotmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | fs/ext4/super.c | 22 |
1 files changed, 10 insertions, 12 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 830160ad07a63..f7c20bb20da37 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2034,6 +2034,16 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token, #endif } else if (token == Opt_dax) { #ifdef CONFIG_FS_DAX + if (is_remount && test_opt(sb, DAX)) { + ext4_msg(sb, KERN_ERR, "can't mount with " + "both data=journal and dax"); + return -1; + } + if (is_remount && !(sbi->s_mount_opt & EXT4_MOUNT_DAX)) { + ext4_msg(sb, KERN_ERR, "can't change " + "dax mount option while remounting"); + return -1; + } ext4_msg(sb, KERN_WARNING, "DAX enabled. Warning: EXPERIMENTAL, use at your own risk"); sbi->s_mount_opt |= m->mount_opt; @@ -5367,12 +5377,6 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data) err = -EINVAL; goto restore_opts; } - if (test_opt(sb, DAX)) { - ext4_msg(sb, KERN_ERR, "can't mount with " - "both data=journal and dax"); - err = -EINVAL; - goto restore_opts; - } } else if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_ORDERED_DATA) { if (test_opt(sb, JOURNAL_ASYNC_COMMIT)) { ext4_msg(sb, KERN_ERR, "can't mount with " @@ -5388,12 +5392,6 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data) goto restore_opts; } - if ((sbi->s_mount_opt ^ old_opts.s_mount_opt) & EXT4_MOUNT_DAX) { - ext4_msg(sb, KERN_WARNING, "warning: refusing change of " - "dax flag with busy inodes while remounting"); - sbi->s_mount_opt ^= EXT4_MOUNT_DAX; - } - if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED) ext4_abort(sb, "Abort forced by user"); |