bh returned by ext4_read_block_bitmap_nowait() might be NULL, validate
the bh pointer before using it.
I've seen this in fsfuzz testing.
EXT4-fs error (device loop0): ext4_read_block_bitmap_nowait:385: comm touch: Cannot get buffer for block bitmap - block_group = 0, block_bitmap = 3925999616
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff8121de25>] ext4_wait_block_bitmap+0x25/0xe0
...
Call Trace:
[<ffffffff8121e1e5>] ext4_read_block_bitmap+0x35/0x60
[<ffffffff8125e9c6>] ext4_free_blocks+0x236/0xb80
[<ffffffff811d0d36>] ? __getblk+0x36/0x70
[<ffffffff811d0a5f>] ? __find_get_block+0x8f/0x210
[<ffffffff81191ef3>] ? kmem_cache_free+0x33/0x140
[<ffffffff812678e5>] ext4_xattr_release_block+0x1b5/0x1d0
[<ffffffff812679be>] ext4_xattr_delete_inode+0xbe/0x100
[<ffffffff81222a7c>] ext4_free_inode+0x7c/0x4d0
[<ffffffff812277b8>] ? ext4_mark_inode_dirty+0x88/0x230
[<ffffffff8122993c>] ext4_evict_inode+0x32c/0x490
[<ffffffff811b8cd7>] evict+0xa7/0x1c0
[<ffffffff811b8ed3>] iput_final+0xe3/0x170
[<ffffffff811b8f9e>] iput+0x3e/0x50
[<ffffffff812316fd>] ext4_add_nondir+0x4d/0x90
[<ffffffff81231d0b>] ext4_create+0xeb/0x170
[<ffffffff811aae9c>] vfs_create+0xac/0xd0
[<ffffffff811ac845>] lookup_open+0x185/0x1c0
[<ffffffff8129e3b9>] ? selinux_inode_permission+0xa9/0x170
[<ffffffff811acb54>] do_last+0x2d4/0x7a0
[<ffffffff811af743>] path_openat+0xb3/0x480
[<ffffffff8116a8a1>] ? handle_mm_fault+0x251/0x3b0
[<ffffffff811afc49>] do_filp_open+0x49/0xa0
[<ffffffff811bbaad>] ? __alloc_fd+0xdd/0x150
[<ffffffff8119da28>] do_sys_open+0x108/0x1f0
[<ffffffff8119db51>] sys_open+0x21/0x30
[<ffffffff81618959>] system_call_fastpath+0x16/0x1b
Also fix comment for ext4_read_block_bitmap_nowait()
Cc: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Eryu Guan <guaneryu@xxxxxxxxx>
---
fs/ext4/balloc.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index cf18217..33938c1 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -358,7 +358,7 @@ void ext4_validate_block_bitmap(struct super_block *sb,
}
/**
- * ext4_read_block_bitmap()
+ * ext4_read_block_bitmap_nowait()
* @sb: super block
* @block_group: given block group
*
@@ -457,6 +457,8 @@ ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
struct buffer_head *bh;
bh = ext4_read_block_bitmap_nowait(sb, block_group);
+ if (!bh)
+ return NULL;
if (ext4_wait_block_bitmap(sb, block_group, bh)) {
put_bh(bh);
return NULL;
--
1.7.11.7
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