bfs: add sanity check at bfs_fill_super()

Tetsuo Handa · torvalds · commit 9f2df09a33aa · 2018-11-03T10:09:38.000-07:00
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@I-love.SAKURA.ne.jp Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Reported-by: syzbot <syzbot+71c6b5d68e91149fc8a4@syzkaller.appspotmail.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Tigran Aivazian <aivazian.tigran@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git 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) {
 		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;
+	}
 	for (i = 0; i < BFS_ROOT_INO; i++)
 		set_bit(i, info->si_imap);
 
