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ext4: fix use-after-free race with debug_want_extra_isize

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When remounting with debug_want_extra_isize, we were not performing the
same checks that we do during a normal mount.  That allowed us to set a
value for s_want_extra_isize that reached outside the s_inode_size.

Fixes: e2b911c535 ("ext4: clean up feature test macros with predicate functions")
Reported-by: syzbot+f584efa0ac7213c226b7@syzkaller.appspotmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Barret Rhoden <brho@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
This commit is contained in:
Barret Rhoden 2019-04-25 11:55:50 -04:00 committed by Theodore Ts'o
parent 8c380ab4b7
commit 7bc04c5c2c
1 changed files with 34 additions and 24 deletions
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58
fs/ext4/super.c
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@ -3513,6 +3513,37 @@ int ext4_calculate_overhead(struct super_block *sb)
return 0;
}
static void ext4_clamp_want_extra_isize(struct super_block *sb)
{
struct ext4_sb_info *sbi = EXT4_SB(sb);
struct ext4_super_block *es = sbi->s_es;
/* determine the minimum size of new large inodes, if present */
if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE &&
sbi->s_want_extra_isize == 0) {
sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
EXT4_GOOD_OLD_INODE_SIZE;
if (ext4_has_feature_extra_isize(sb)) {
if (sbi->s_want_extra_isize <
le16_to_cpu(es->s_want_extra_isize))
sbi->s_want_extra_isize =
le16_to_cpu(es->s_want_extra_isize);
if (sbi->s_want_extra_isize <
le16_to_cpu(es->s_min_extra_isize))
sbi->s_want_extra_isize =
le16_to_cpu(es->s_min_extra_isize);
}
}
/* Check if enough inode space is available */
if (EXT4_GOOD_OLD_INODE_SIZE + sbi->s_want_extra_isize >
sbi->s_inode_size) {
sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
EXT4_GOOD_OLD_INODE_SIZE;
ext4_msg(sb, KERN_INFO,
"required extra inode space not available");
}
}
static void ext4_set_resv_clusters(struct super_block *sb)
{
ext4_fsblk_t resv_clusters;
@ -4387,30 +4418,7 @@ no_journal:
} else if (ret)
goto failed_mount4a;
/* determine the minimum size of new large inodes, if present */
if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE &&
sbi->s_want_extra_isize == 0) {
sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
EXT4_GOOD_OLD_INODE_SIZE;
if (ext4_has_feature_extra_isize(sb)) {
if (sbi->s_want_extra_isize <
le16_to_cpu(es->s_want_extra_isize))
sbi->s_want_extra_isize =
le16_to_cpu(es->s_want_extra_isize);
if (sbi->s_want_extra_isize <
le16_to_cpu(es->s_min_extra_isize))
sbi->s_want_extra_isize =
le16_to_cpu(es->s_min_extra_isize);
}
}
/* Check if enough inode space is available */
if (EXT4_GOOD_OLD_INODE_SIZE + sbi->s_want_extra_isize >
sbi->s_inode_size) {
sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
EXT4_GOOD_OLD_INODE_SIZE;
ext4_msg(sb, KERN_INFO, "required extra inode space not"
"available");
}
ext4_clamp_want_extra_isize(sb);
ext4_set_resv_clusters(sb);
@ -5194,6 +5202,8 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
goto restore_opts;
}
ext4_clamp_want_extra_isize(sb);
if ((old_opts.s_mount_opt & EXT4_MOUNT_JOURNAL_CHECKSUM) ^
test_opt(sb, JOURNAL_CHECKSUM)) {
ext4_msg(sb, KERN_ERR, "changing journal_checksum "