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ext4: validate the debug_want_extra_isize mount option at parse time
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Instead of setting s_want_extra_size and then making sure that it is a
valid value afterwards, validate the field before we set it.  This
avoids races and other problems when remounting the file system.

Link: https://lore.kernel.org/r/20191215063020.GA11512@mit.edu
Cc: stable@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reported-and-tested-by: syzbot+4a39a025912b265cacef@syzkaller.appspotmail.com
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Theodore Ts'o committed Dec 15, 2019
1 parent a70fd5a commit 9803387
Showing 1 changed file with 69 additions and 74 deletions.
143 changes: 69 additions & 74 deletions fs/ext4/super.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1886,6 +1886,13 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
}
sbi->s_commit_interval = HZ * arg;
} else if (token == Opt_debug_want_extra_isize) {
if ((arg & 1) ||
(arg < 4) ||
(arg > (sbi->s_inode_size - EXT4_GOOD_OLD_INODE_SIZE))) {
ext4_msg(sb, KERN_ERR,
"Invalid want_extra_isize %d", arg);
return -1;
}
sbi->s_want_extra_isize = arg;
} else if (token == Opt_max_batch_time) {
sbi->s_max_batch_time = arg;
Expand Down Expand Up @@ -3540,40 +3547,6 @@ 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;
unsigned def_extra_isize = sizeof(struct ext4_inode) -
EXT4_GOOD_OLD_INODE_SIZE;

if (sbi->s_inode_size == EXT4_GOOD_OLD_INODE_SIZE) {
sbi->s_want_extra_isize = 0;
return;
}
if (sbi->s_want_extra_isize < 4) {
sbi->s_want_extra_isize = def_extra_isize;
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 ((sbi->s_want_extra_isize > sbi->s_inode_size) ||
(EXT4_GOOD_OLD_INODE_SIZE + sbi->s_want_extra_isize >
sbi->s_inode_size)) {
sbi->s_want_extra_isize = def_extra_isize;
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;
Expand Down Expand Up @@ -3781,6 +3754,68 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
*/
sbi->s_li_wait_mult = EXT4_DEF_LI_WAIT_MULT;

if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV) {
sbi->s_inode_size = EXT4_GOOD_OLD_INODE_SIZE;
sbi->s_first_ino = EXT4_GOOD_OLD_FIRST_INO;
} else {
sbi->s_inode_size = le16_to_cpu(es->s_inode_size);
sbi->s_first_ino = le32_to_cpu(es->s_first_ino);
if (sbi->s_first_ino < EXT4_GOOD_OLD_FIRST_INO) {
ext4_msg(sb, KERN_ERR, "invalid first ino: %u",
sbi->s_first_ino);
goto failed_mount;
}
if ((sbi->s_inode_size < EXT4_GOOD_OLD_INODE_SIZE) ||
(!is_power_of_2(sbi->s_inode_size)) ||
(sbi->s_inode_size > blocksize)) {
ext4_msg(sb, KERN_ERR,
"unsupported inode size: %d",
sbi->s_inode_size);
goto failed_mount;
}
/*
* i_atime_extra is the last extra field available for
* [acm]times in struct ext4_inode. Checking for that
* field should suffice to ensure we have extra space
* for all three.
*/
if (sbi->s_inode_size >= offsetof(struct ext4_inode, i_atime_extra) +
sizeof(((struct ext4_inode *)0)->i_atime_extra)) {
sb->s_time_gran = 1;
sb->s_time_max = EXT4_EXTRA_TIMESTAMP_MAX;
} else {
sb->s_time_gran = NSEC_PER_SEC;
sb->s_time_max = EXT4_NON_EXTRA_TIMESTAMP_MAX;
}
sb->s_time_min = EXT4_TIMESTAMP_MIN;
}
if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE) {
sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
EXT4_GOOD_OLD_INODE_SIZE;
if (ext4_has_feature_extra_isize(sb)) {
unsigned v, max = (sbi->s_inode_size -
EXT4_GOOD_OLD_INODE_SIZE);

v = le16_to_cpu(es->s_want_extra_isize);
if (v > max) {
ext4_msg(sb, KERN_ERR,
"bad s_want_extra_isize: %d", v);
goto failed_mount;
}
if (sbi->s_want_extra_isize < v)
sbi->s_want_extra_isize = v;

v = le16_to_cpu(es->s_min_extra_isize);
if (v > max) {
ext4_msg(sb, KERN_ERR,
"bad s_min_extra_isize: %d", v);
goto failed_mount;
}
if (sbi->s_want_extra_isize < v)
sbi->s_want_extra_isize = v;
}
}

if (sbi->s_es->s_mount_opts[0]) {
char *s_mount_opts = kstrndup(sbi->s_es->s_mount_opts,
sizeof(sbi->s_es->s_mount_opts),
Expand Down Expand Up @@ -4019,42 +4054,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
has_huge_files);
sb->s_maxbytes = ext4_max_size(sb->s_blocksize_bits, has_huge_files);

if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV) {
sbi->s_inode_size = EXT4_GOOD_OLD_INODE_SIZE;
sbi->s_first_ino = EXT4_GOOD_OLD_FIRST_INO;
} else {
sbi->s_inode_size = le16_to_cpu(es->s_inode_size);
sbi->s_first_ino = le32_to_cpu(es->s_first_ino);
if (sbi->s_first_ino < EXT4_GOOD_OLD_FIRST_INO) {
ext4_msg(sb, KERN_ERR, "invalid first ino: %u",
sbi->s_first_ino);
goto failed_mount;
}
if ((sbi->s_inode_size < EXT4_GOOD_OLD_INODE_SIZE) ||
(!is_power_of_2(sbi->s_inode_size)) ||
(sbi->s_inode_size > blocksize)) {
ext4_msg(sb, KERN_ERR,
"unsupported inode size: %d",
sbi->s_inode_size);
goto failed_mount;
}
/*
* i_atime_extra is the last extra field available for [acm]times in
* struct ext4_inode. Checking for that field should suffice to ensure
* we have extra space for all three.
*/
if (sbi->s_inode_size >= offsetof(struct ext4_inode, i_atime_extra) +
sizeof(((struct ext4_inode *)0)->i_atime_extra)) {
sb->s_time_gran = 1;
sb->s_time_max = EXT4_EXTRA_TIMESTAMP_MAX;
} else {
sb->s_time_gran = NSEC_PER_SEC;
sb->s_time_max = EXT4_NON_EXTRA_TIMESTAMP_MAX;
}

sb->s_time_min = EXT4_TIMESTAMP_MIN;
}

sbi->s_desc_size = le16_to_cpu(es->s_desc_size);
if (ext4_has_feature_64bit(sb)) {
if (sbi->s_desc_size < EXT4_MIN_DESC_SIZE_64BIT ||
Expand Down Expand Up @@ -4503,8 +4502,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
} else if (ret)
goto failed_mount4a;

ext4_clamp_want_extra_isize(sb);

ext4_set_resv_clusters(sb);

err = ext4_setup_system_zone(sb);
Expand Down Expand Up @@ -5292,8 +5289,6 @@ 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 "
Expand Down

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