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ext4: check bh in ext4_read_block_bitmap()
Validate the bh pointer before using it, since ext4_read_block_bitmap_nowait() might return NULL. 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() Signed-off-by: Eryu Guan <guaneryu@gmail.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: stable@vger.kernel.org
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@ -358,7 +358,7 @@ void ext4_validate_block_bitmap(struct super_block *sb,
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}
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/**
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* ext4_read_block_bitmap()
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* ext4_read_block_bitmap_nowait()
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* @sb: super block
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* @block_group: given block group
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*
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@ -457,6 +457,8 @@ ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
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struct buffer_head *bh;
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bh = ext4_read_block_bitmap_nowait(sb, block_group);
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if (!bh)
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return NULL;
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if (ext4_wait_block_bitmap(sb, block_group, bh)) {
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put_bh(bh);
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return NULL;
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