From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Subject: bfs: add sanity check at bfs_fill_super() syzbot is reporting too large memory allocation at bfs_fill_super() [1]. Since file system image is corrupted such that bfs_sb->s_start == 0, bfs_fill_super() is trying to allocate 8MB of continuous memory. Fix this by adding a sanity check on bfs_sb->s_start, __GFP_NOWARN and printf(). [1] https://syzkaller.appspot.com/bug?id=16a87c236b951351374a84c8a32f40edbc034e96 Link: http://lkml.kernel.org/r/1525862104-3407-1-git-send-email-penguin-kernel@xxxxxxxxxxxxxxxxxxx Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Reported-by: syzbot <syzbot+71c6b5d68e91149fc8a4@xxxxxxxxxxxxxxxxxxxxxxxxx> Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Tigran Aivazian <aivazian.tigran@xxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/bfs/inode.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) --- a/fs/bfs/inode.c~bfs-add-sanity-check-at-bfs_fill_super +++ a/fs/bfs/inode.c @@ -350,7 +350,8 @@ static int bfs_fill_super(struct super_b s->s_magic = BFS_MAGIC; - if (le32_to_cpu(bfs_sb->s_start) > le32_to_cpu(bfs_sb->s_end)) { + if (le32_to_cpu(bfs_sb->s_start) > le32_to_cpu(bfs_sb->s_end) || + le32_to_cpu(bfs_sb->s_start) < BFS_BSIZE) { printf("Superblock is corrupted\n"); goto out1; } @@ -359,9 +360,11 @@ static int bfs_fill_super(struct super_b sizeof(struct bfs_inode) + BFS_ROOT_INO - 1; imap_len = (info->si_lasti / 8) + 1; - info->si_imap = kzalloc(imap_len, GFP_KERNEL); - if (!info->si_imap) + info->si_imap = kzalloc(imap_len, GFP_KERNEL | __GFP_NOWARN); + if (!info->si_imap) { + printf("Cannot allocate %u bytes\n", imap_len); goto out1; + } for (i = 0; i < BFS_ROOT_INO; i++) set_bit(i, info->si_imap); _
