From: Zhihao Cheng chengzhihao1@huawei.com
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 --- fs/quota/quota_tree.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+)
--- a/fs/quota/quota_tree.c +++ b/fs/quota/quota_tree.c @@ -80,6 +80,35 @@ static ssize_t write_blk(struct qtree_me 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_m 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 qtr *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 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);