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authorZhang Yi <yi.zhang@huawei.com>2022-06-01 17:27:17 +0800
committerTheodore Ts'o <tytso@mit.edu>2022-06-18 19:36:08 -0400
commitb55c3cd102a6f48b90e61c44f7f3dda8c290c694 (patch)
treef52b14a46633d8b38fb775dda349df54096b9a60 /fs/ext4
parentbc75a6eb856cb1507fa907bf6c1eda91b3fef52f (diff)
ext4: add reserved GDT blocks check
We capture a NULL pointer issue when resizing a corrupt ext4 image which is freshly clear resize_inode feature (not run e2fsck). It could be simply reproduced by following steps. The problem is because of the resize_inode feature was cleared, and it will convert the filesystem to meta_bg mode in ext4_resize_fs(), but the es->s_reserved_gdt_blocks was not reduced to zero, so could we mistakenly call reserve_backup_gdb() and passing an uninitialized resize_inode to it when adding new group descriptors. mkfs.ext4 /dev/sda 3G tune2fs -O ^resize_inode /dev/sda #forget to run requested e2fsck mount /dev/sda /mnt resize2fs /dev/sda 8G ======== BUG: kernel NULL pointer dereference, address: 0000000000000028 CPU: 19 PID: 3243 Comm: resize2fs Not tainted 5.18.0-rc7-00001-gfde086c5ebfd #748 ... RIP: 0010:ext4_flex_group_add+0xe08/0x2570 ... Call Trace: <TASK> ext4_resize_fs+0xbec/0x1660 __ext4_ioctl+0x1749/0x24e0 ext4_ioctl+0x12/0x20 __x64_sys_ioctl+0xa6/0x110 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f2dd739617b ======== The fix is simple, add a check in ext4_resize_begin() to make sure that the es->s_reserved_gdt_blocks is zero when the resize_inode feature is disabled. Cc: stable@kernel.org Signed-off-by: Zhang Yi <yi.zhang@huawei.com> Reviewed-by: Ritesh Harjani <ritesh.list@gmail.com> Reviewed-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20220601092717.763694-1-yi.zhang@huawei.com Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/ext4')
-rw-r--r--fs/ext4/resize.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 90a941d20dff..8b70a4701293 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -54,6 +54,16 @@ int ext4_resize_begin(struct super_block *sb)
return -EPERM;
/*
+ * If the reserved GDT blocks is non-zero, the resize_inode feature
+ * should always be set.
+ */
+ if (EXT4_SB(sb)->s_es->s_reserved_gdt_blocks &&
+ !ext4_has_feature_resize_inode(sb)) {
+ ext4_error(sb, "resize_inode disabled but reserved GDT blocks non-zero");
+ return -EFSCORRUPTED;
+ }
+
+ /*
* If we are not using the primary superblock/GDT copy don't resize,
* because the user tools have no way of handling this. Probably a
* bad time to do it anyways.