From 83f99de1b7c0dcfa42b211e5e40334b7ad786b36 Mon Sep 17 00:00:00 2001 From: Ye Bin Date: Tue, 15 Aug 2023 19:26:11 +0800 Subject: [PATCH] ext2: fix race between setxattr and write back There's an issue when allocating xattrs 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: 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 doesn't allocate new blocks so for these cases we may be allocating blocks during writeback. However, there is no protection between ext2_xattr_set() and do_writepages() so these two functions can conflict on handling the reservation window. To solve about issue don't use the reservation window when allocating block for xattr. Signed-off-by: Ye Bin Message-Id: <20230815112612.221145-4-yebin10@huawei.com> Signed-off-by: Jan Kara --- fs/ext2/balloc.c | 14 +++++++------- fs/ext2/xattr.c | 3 ++- 2 files changed, 9 insertions(+), 8 deletions(-) diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c index a9648c3137db..dd74c77a4ac1 100644 --- a/fs/ext2/balloc.c +++ b/fs/ext2/balloc.c @@ -1244,15 +1244,15 @@ ext2_fsblk_t ext2_new_blocks(struct inode *inode, ext2_fsblk_t goal, es = EXT2_SB(sb)->s_es; ext2_debug("goal=%lu.\n", goal); /* - * Allocate a block from reservation only when - * filesystem is mounted with reservation(default,-o reservation), and - * 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) + * Allocate a block from reservation only when the filesystem is + * mounted with reservation(default,-o reservation), and 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). Also do not use the + * reservation window if the caller asked us not to do it. */ block_i = EXT2_I(inode)->i_block_alloc_info; - if (block_i) { + if (!(flags & EXT2_ALLOC_NORESERVE) && block_i) { windowsz = block_i->rsv_window_node.rsv_goal_size; if (windowsz > 0) my_rsv = &block_i->rsv_window_node; diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c index 3b4ff6974ab8..b7c64fc1c008 100644 --- a/fs/ext2/xattr.c +++ b/fs/ext2/xattr.c @@ -744,7 +744,8 @@ ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh, EXT2_I(inode)->i_block_group); unsigned long count = 1; ext2_fsblk_t block = ext2_new_blocks(inode, goal, - &count, &error, 0); + &count, &error, + EXT2_ALLOC_NORESERVE); if (error) goto cleanup; ea_idebug(inode, "creating block %lu", block);