From: Tadeusz Struk <tadeusz.struk@xxxxxxxxxx> commit 2da376228a2427501feb9d15815a45dbdbdd753e upstream. Syzbot found an issue [1] in ext4_fallocate(). The C reproducer [2] calls fallocate(), passing size 0xffeffeff000ul, and offset 0x1000000ul, which, when added together exceed the bitmap_maxbytes for the inode. This triggers a BUG in ext4_ind_remove_space(). According to the comments in this function the 'end' parameter needs to be one block after the last block to be removed. In the case when the BUG is triggered it points to the last block. Modify the ext4_punch_hole() function and add constraint that caps the length to satisfy the one before laster block requirement. LINK: [1] https://syzkaller.appspot.com/bug?id=b80bd9cf348aac724a4f4dff251800106d721331 LINK: [2] https://syzkaller.appspot.com/text?tag=ReproC&x=14ba0238700000 Fixes: a4bb6b64e39a ("ext4: enable "punch hole" functionality") Reported-by: syzbot+7a806094edd5d07ba029@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Tadeusz Struk <tadeusz.struk@xxxxxxxxxx> Link: https://lore.kernel.org/r/20220331200515.153214-1-tadeusz.struk@xxxxxxxxxx Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Cc: stable@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/ext4/inode.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4224,7 +4224,8 @@ int ext4_punch_hole(struct inode *inode, struct super_block *sb = inode->i_sb; ext4_lblk_t first_block, stop_block; struct address_space *mapping = inode->i_mapping; - loff_t first_block_offset, last_block_offset; + loff_t first_block_offset, last_block_offset, max_length; + struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); handle_t *handle; unsigned int credits; int ret = 0; @@ -4270,6 +4271,14 @@ int ext4_punch_hole(struct inode *inode, offset; } + /* + * For punch hole the length + offset needs to be within one block + * before last range. Adjust the length if it goes beyond that limit. + */ + max_length = sbi->s_bitmap_maxbytes - inode->i_sb->s_blocksize; + if (offset + length > max_length) + length = max_length - offset; + if (offset & (sb->s_blocksize - 1) || (offset + length) & (sb->s_blocksize - 1)) { /*
