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Date: Tue, 15 Aug 2023 19:26:11 +0800
From: Ye Bin <yebin10@...wei.com>
To: <jack@...e.cz>, <linux-ext4@...r.kernel.org>
CC: <linux-kernel@...r.kernel.org>, Ye Bin <yebin10@...wei.com>
Subject: [PATCH v2 3/4] ext2: fix race between setxattr and write back
There's a issue as follows:
Block Allocation Reservation Windows Map (ext2_try_to_allocate_with_rsv):
reservation window 0x000000006f105382 start: 0, end: 0
reservation window 0x000000008fd1a555 start: 1044, end: 1059
Window map complete.
kernel BUG at fs/ext2/balloc.c:1158!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
RIP: 0010:ext2_try_to_allocate_with_rsv.isra.0+0x15c4/0x1800
Call Trace:
<TASK>
ext2_new_blocks+0x935/0x1690
ext2_new_block+0x73/0xa0
ext2_xattr_set2+0x74f/0x1730
ext2_xattr_set+0x12b6/0x2260
ext2_xattr_user_set+0x9c/0x110
__vfs_setxattr+0x139/0x1d0
__vfs_setxattr_noperm+0xfc/0x370
__vfs_setxattr_locked+0x205/0x2c0
vfs_setxattr+0x19d/0x3b0
do_setxattr+0xff/0x220
setxattr+0x123/0x150
path_setxattr+0x193/0x1e0
__x64_sys_setxattr+0xc8/0x170
do_syscall_64+0x35/0x80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
Above issue may happens as follows:
setxattr write back
ext2_xattr_set
ext2_xattr_set2
ext2_new_block
ext2_new_blocks
ext2_try_to_allocate_with_rsv
alloc_new_reservation
--> group=0 [0, 1023] rsv [1016, 1023]
do_writepages
mpage_writepages
write_cache_pages
__mpage_writepage
ext2_get_block
ext2_get_blocks
ext2_alloc_branch
ext2_new_blocks
ext2_try_to_allocate_with_rsv
alloc_new_reservation
-->group=1 [1024, 2047] rsv [1044, 1059]
if ((my_rsv->rsv_start > group_last_block) ||
(my_rsv->rsv_end < group_first_block)
rsv_window_dump
BUG();
Now ext2 mkwrite delay allocate new blocks. So there maybe allocate blocks when
do write back. However, there is no concurrent protection between
ext2_xattr_set() and do_writepages().
To solve about issue don't use reservation window when allocate block for xattr.
Signed-off-by: Ye Bin <yebin10@...wei.com>
---
fs/ext2/balloc.c | 15 +++++++++------
fs/ext2/xattr.c | 4 ++--
2 files changed, 11 insertions(+), 8 deletions(-)
diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
index 99a19f2ecd6f..4ff1d831bb80 100644
--- a/fs/ext2/balloc.c
+++ b/fs/ext2/balloc.c
@@ -1247,13 +1247,16 @@ ext2_fsblk_t ext2_new_blocks(struct inode *inode, ext2_fsblk_t goal,
* it's a regular file, and
* the desired window size is greater than 0 (One could use ioctl
* command EXT2_IOC_SETRSVSZ to set the window size to 0 to turn off
- * reservation on that particular file)
+ * reservation on that particular file), and unspecified Do not use
+ * reservation window.
*/
- block_i = EXT2_I(inode)->i_block_alloc_info;
- if (block_i) {
- windowsz = block_i->rsv_window_node.rsv_goal_size;
- if (windowsz > 0)
- my_rsv = &block_i->rsv_window_node;
+ if (!(flag & EXT2_ALLOC_NORESERVE)) {
+ block_i = EXT2_I(inode)->i_block_alloc_info;
+ if (block_i) {
+ windowsz = block_i->rsv_window_node.rsv_goal_size;
+ if (windowsz > 0)
+ my_rsv = &block_i->rsv_window_node;
+ }
}
if (!ext2_has_free_blocks(sbi)) {
diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
index e076386a26f4..21725b8d04c8 100644
--- a/fs/ext2/xattr.c
+++ b/fs/ext2/xattr.c
@@ -743,8 +743,8 @@ ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
ext2_fsblk_t goal = ext2_group_first_block_no(sb,
EXT2_I(inode)->i_block_group);
unsigned long count = 1;
- int block = ext2_new_blocks(inode, goal, &count,
- &error, 0);
+ int block = ext2_new_blocks(inode, goal, &count, &error,
+ EXT2_ALLOC_NORESERVE);
if (error)
goto cleanup;
ea_idebug(inode, "creating block %d", block);
--
2.31.1
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