Commit 9f2df09a authored Nov 02, 2018 by Tetsuo Handa Committed by Linus Torvalds Nov 03, 2018

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@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>

parent 6f0483d1

fs/bfs/inode.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -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);

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