From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f67.google.com ([74.125.82.67]:34247 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755128AbeFNML4 (ORCPT ); Thu, 14 Jun 2018 08:11:56 -0400 Received: by mail-wm0-f67.google.com with SMTP id l15-v6so2893033wmc.1 for ; Thu, 14 Jun 2018 05:11:55 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <19e36f90-d17e-ca6f-2c6e-11a712dc6d21@i-love.sakura.ne.jp> References: <1525862104-3407-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20180509160658.c37bef542a8ee5245a13917b@linux-foundation.org> <201805092346.w49NkINl045657@www262.sakura.ne.jp> <20180509165321.3b2b1313fde0f007c1a5a015@linux-foundation.org> <9ef86114-02d6-b243-203d-fbbdab95a6fa@I-love.SAKURA.ne.jp> <19e36f90-d17e-ca6f-2c6e-11a712dc6d21@i-love.sakura.ne.jp> From: Tigran Aivazian Date: Thu, 14 Jun 2018 13:11:54 +0100 Message-ID: Subject: Re: [PATCH] bfs: add sanity check at bfs_fill_super(). To: Tetsuo Handa Cc: Andrew Morton , linux-fsdevel@vger.kernel.org, syzbot , syzkaller-bugs Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Thank you. Please see comments below: On 14 June 2018 at 11:45, Tetsuo Handa wrote: > (Which patch did you mean? Hmm, I paste both patches instead of waiting for your answer.) I only meant the BFS patch. > commit 0c54bbdb89992eeff50866b64366a1a0cbd0e6fb > Author: Tetsuo Handa > Date: Sat May 26 14:15:41 2018 +1000 > > 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 > Reported-by: syzbot > Reviewed-by: Andrew Morton > Cc: Tigran Aivazian > Cc: Matthew Wilcox > Signed-off-by: Andrew Morton > Signed-off-by: Stephen Rothwell > > 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; > } Yes, this is acceptable. > @@ -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 is unnecessary. As Andrew Morton pointed out, if people set panic_on_warn then they do really want a panic on allocation failure warnings. Please update the patch with just the above sanity check for s_start < BFS_BSIZE. Kind regards, Tigran