On Wed, 9 May 2018 19:35:04 +0900 Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > 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 > > ... > > --- a/fs/bfs/inode.c > +++ b/fs/bfs/inode.c > @@ -350,7 +350,8 @@ static int bfs_fill_super(struct super_block *s, void *data, int silent) > > 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) { hm, how did you figure out that s_start cannot be less than BFS_BSIZE? >From this, I guess? info->si_lasti = (le32_to_cpu(bfs_sb->s_start) - BFS_BSIZE) / I wonder if this is the most appropriate way to check. > printf("Superblock is corrupted\n"); > goto out1; > } > @@ -359,9 +360,11 @@ static int bfs_fill_super(struct super_block *s, void *data, int silent) > 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; > + } This seems unnecessary - if the kzalloc() fails we'll get the page-allocation-fauilure warning and a nice backtrace, etc. Why suppress all of that and add our custom warning instead?
