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author | Zhihao Cheng <chengzhihao1@huawei.com> | 2022-09-23 16:45:52 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-10-26 14:25:09 +0300 |
commit | 6b7ae4a904a4dd83cae245c02db88c8b5d49e1cb (patch) | |
tree | 9cc6dce5df198ec8bb5880bb2c941db5004aeaa9 /fs | |
parent | 5b1a56beb6b8069422a10bb57f3abfa4f4871bc4 (diff) | |
download | linux-6b7ae4a904a4dd83cae245c02db88c8b5d49e1cb.tar.xz |
quota: Check next/prev free block number after reading from quota file
commit 6c8ea8b8cd4722efd419f91ca46a2dc81b7d89a3 upstream.
Following process:
Init: v2_read_file_info: <3> dqi_free_blk 0 dqi_free_entry 5 dqi_blks 6
Step 1. chown bin f_a -> dquot_acquire -> v2_write_dquot:
qtree_write_dquot
do_insert_tree
find_free_dqentry
get_free_dqblk
write_blk(info->dqi_blocks) // info->dqi_blocks = 6, failure. The
content in physical block (corresponding to blk 6) is random.
Step 2. chown root f_a -> dquot_transfer -> dqput_all -> dqput ->
ext4_release_dquot -> v2_release_dquot -> qtree_delete_dquot:
dquot_release
remove_tree
free_dqentry
put_free_dqblk(6)
info->dqi_free_blk = blk // info->dqi_free_blk = 6
Step 3. drop cache (buffer head for block 6 is released)
Step 4. chown bin f_b -> dquot_acquire -> commit_dqblk -> v2_write_dquot:
qtree_write_dquot
do_insert_tree
find_free_dqentry
get_free_dqblk
dh = (struct qt_disk_dqdbheader *)buf
blk = info->dqi_free_blk // 6
ret = read_blk(info, blk, buf) // The content of buf is random
info->dqi_free_blk = le32_to_cpu(dh->dqdh_next_free) // random blk
Step 5. chown bin f_c -> notify_change -> ext4_setattr -> dquot_transfer:
dquot = dqget -> acquire_dquot -> ext4_acquire_dquot -> dquot_acquire ->
commit_dqblk -> v2_write_dquot -> dq_insert_tree:
do_insert_tree
find_free_dqentry
get_free_dqblk
blk = info->dqi_free_blk // If blk < 0 and blk is not an error
code, it will be returned as dquot
transfer_to[USRQUOTA] = dquot // A random negative value
__dquot_transfer(transfer_to)
dquot_add_inodes(transfer_to[cnt])
spin_lock(&dquot->dq_dqb_lock) // page fault
, which will lead to kernel page fault:
Quota error (device sda): qtree_write_dquot: Error -8000 occurred
while creating quota
BUG: unable to handle page fault for address: ffffffffffffe120
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
Oops: 0002 [#1] PREEMPT SMP
CPU: 0 PID: 5974 Comm: chown Not tainted 6.0.0-rc1-00004
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
RIP: 0010:_raw_spin_lock+0x3a/0x90
Call Trace:
dquot_add_inodes+0x28/0x270
__dquot_transfer+0x377/0x840
dquot_transfer+0xde/0x540
ext4_setattr+0x405/0x14d0
notify_change+0x68e/0x9f0
chown_common+0x300/0x430
__x64_sys_fchownat+0x29/0x40
In order to avoid accessing invalid quota memory address, this patch adds
block number checking of next/prev free block read from quota file.
Fetch a reproducer in [Link].
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216372
Fixes: 1da177e4c3f4152 ("Linux-2.6.12-rc2")
CC: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20220923134555.2623931-2-chengzhihao1@huawei.com
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/quota/quota_tree.c | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/fs/quota/quota_tree.c b/fs/quota/quota_tree.c index 1a188fbdf34e..07948f6ac84e 100644 --- a/fs/quota/quota_tree.c +++ b/fs/quota/quota_tree.c @@ -80,6 +80,35 @@ static ssize_t write_blk(struct qtree_mem_dqinfo *info, uint blk, char *buf) return ret; } +static inline int do_check_range(struct super_block *sb, const char *val_name, + uint val, uint min_val, uint max_val) +{ + if (val < min_val || val > max_val) { + quota_error(sb, "Getting %s %u out of range %u-%u", + val_name, val, min_val, max_val); + return -EUCLEAN; + } + + return 0; +} + +static int check_dquot_block_header(struct qtree_mem_dqinfo *info, + struct qt_disk_dqdbheader *dh) +{ + int err = 0; + + err = do_check_range(info->dqi_sb, "dqdh_next_free", + le32_to_cpu(dh->dqdh_next_free), 0, + info->dqi_blocks - 1); + if (err) + return err; + err = do_check_range(info->dqi_sb, "dqdh_prev_free", + le32_to_cpu(dh->dqdh_prev_free), 0, + info->dqi_blocks - 1); + + return err; +} + /* Remove empty block from list and return it */ static int get_free_dqblk(struct qtree_mem_dqinfo *info) { @@ -94,6 +123,9 @@ static int get_free_dqblk(struct qtree_mem_dqinfo *info) ret = read_blk(info, blk, buf); if (ret < 0) goto out_buf; + ret = check_dquot_block_header(info, dh); + if (ret) + goto out_buf; info->dqi_free_blk = le32_to_cpu(dh->dqdh_next_free); } else { @@ -241,6 +273,9 @@ static uint find_free_dqentry(struct qtree_mem_dqinfo *info, *err = read_blk(info, blk, buf); if (*err < 0) goto out_buf; + *err = check_dquot_block_header(info, dh); + if (*err) + goto out_buf; } else { blk = get_free_dqblk(info); if ((int)blk < 0) { @@ -433,6 +468,9 @@ static int free_dqentry(struct qtree_mem_dqinfo *info, struct dquot *dquot, goto out_buf; } dh = (struct qt_disk_dqdbheader *)buf; + ret = check_dquot_block_header(info, dh); + if (ret) + goto out_buf; le16_add_cpu(&dh->dqdh_entries, -1); if (!le16_to_cpu(dh->dqdh_entries)) { /* Block got free? */ ret = remove_free_dqentry(info, buf, blk); |