[PATCH 5.10 77/93] ext4: limit the number of blocks in one ADD_RANGE TLV

Greg Kroah-Hartman
2021-10-04T13:25:37Z

From: Hou Tao <houtao1@huawei.com>

commit a2c2f0826e2b75560b31daf1cd9a755ab93cf4c6 upstream.

Now EXT4_FC_TAG_ADD_RANGE uses ext4_extent to track the
newly-added blocks, but the limit on the max value of
ee_len field is ignored, and it can lead to BUG_ON as
shown below when running command "fallocate -l 128M file"
on a fast_commit-enabled fs:

kernel BUG at fs/ext4/ext4_extents.h:199!
invalid opcode: 0000 [#1] SMP PTI
CPU: 3 PID: 624 Comm: fallocate Not tainted 5.14.0-rc6+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
RIP: 0010:ext4_fc_write_inode_data+0x1f3/0x200
Call Trace:
? ext4_fc_write_inode+0xf2/0x150
ext4_fc_commit+0x93b/0xa00
? ext4_fallocate+0x1ad/0x10d0
ext4_sync_file+0x157/0x340
? ext4_sync_file+0x157/0x340
vfs_fsync_range+0x49/0x80
do_fsync+0x3d/0x70
__x64_sys_fsync+0x14/0x20
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x44/0xae

Simply fixing it by limiting the number of blocks
in one EXT4_FC_TAG_ADD_RANGE TLV.

Fixes: aa75f4d3daae ("ext4: main fast-commit commit path")
Cc: stable@kernel.org
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Link: https://lore.kernel.org/r/20210820044505.474318-1-houtao1@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ext4/fast_commit.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/fs/ext4/fast_commit.c
+++ b/fs/ext4/fast_commit.c
@@ -832,6 +832,12 @@ static int ext4_fc_write_inode_data(stru
sizeof(lrange), (u8 *)&lrange, crc))
return -ENOSPC;
} else {
+ unsigned int max = (map.m_flags & EXT4_MAP_UNWRITTEN) ?
+ EXT_UNWRITTEN_MAX_LEN : EXT_INIT_MAX_LEN;
+
+ /* Limit the number of blocks in one extent */
+ map.m_len = min(max, map.m_len);
+
fc_ext.fc_ino = cpu_to_le32(inode->i_ino);
ex = (struct ext4_extent *)&fc_ext.fc_ex;
ex->ee_block = cpu_to_le32(map.m_lblk);