From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: syzbot <syzbot+71c6b5d68e91149fc8a4@syzkaller.appspotmail.com>,
aivazian.tigran@gmail.com, linux-kernel@vger.kernel.org,
syzkaller-bugs@googlegroups.com
Subject: Re: WARNING: kmalloc bug in bfs_fill_super
Date: Tue, 1 May 2018 19:01:08 +0900 [thread overview]
Message-ID: <32e853dd-3340-653e-a876-dce5de44d990@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <0000000000001f05330568a6b369@google.com>
>From 247cae4da0490c2e285e0a99e630ef963fabb6d5 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Tue, 1 May 2018 14:15:19 +0900
Subject: [PATCH] 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
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+71c6b5d68e91149fc8a4@syzkaller.appspotmail.com>
Cc: Tigran A. Aivazian <aivazian.tigran@gmail.com>
---
fs/bfs/inode.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/fs/bfs/inode.c b/fs/bfs/inode.c
index 9a69392..d81c148 100644
--- 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);
--
1.8.3.1
next prev parent reply other threads:[~2018-05-01 10:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-30 20:01 WARNING: kmalloc bug in bfs_fill_super syzbot
2018-05-01 10:01 ` Tetsuo Handa [this message]
2018-05-01 10:45 ` Tigran Aivazian
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