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Date: Wed, 15 May 2024 04:39:53 +0000
From: Jaegeuk Kim <jaegeuk@kernel.org>
To: Chao Yu <chao@kernel.org>
Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org,
	syzbot+848062ba19c8782ca5c8@syzkaller.appspotmail.com
Subject: Re: [PATCH 3/3] f2fs: fix to do sanity check on i_nid for
 inline_data inode
Message-ID: <ZkQ8mSYP50Etp0-C@google.com>
References: <20240506103313.773503-1-chao@kernel.org>
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 <948ecc86-63f5-48bb-b71c-61d57cbf446c@kernel.org>
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On 05/15, Chao Yu wrote:
> On 2024/5/15 0:07, Jaegeuk Kim wrote:
> > 外部邮件/External Mail
> > 
> > 
> > On 05/11, Chao Yu wrote:
> > > On 2024/5/11 8:38, Jaegeuk Kim wrote:
> > > > On 05/10, Chao Yu wrote:
> > > > > On 2024/5/10 11:36, Jaegeuk Kim wrote:
> > > > > > On 05/10, Chao Yu wrote:
> > > > > > > On 2024/5/9 23:52, Jaegeuk Kim wrote:
> > > > > > > > On 05/06, Chao Yu wrote:
> > > > > > > > > syzbot reports a f2fs bug as below:
> > > > > > > > > 
> > > > > > > > > ------------[ cut here ]------------
> > > > > > > > > kernel BUG at fs/f2fs/inline.c:258!
> > > > > > > > > CPU: 1 PID: 34 Comm: kworker/u8:2 Not tainted 6.9.0-rc6-syzkaller-00012-g9e4bc4bcae01 #0
> > > > > > > > > RIP: 0010:f2fs_write_inline_data+0x781/0x790 fs/f2fs/inline.c:258
> > > > > > > > > Call Trace:
> > > > > > > > >      f2fs_write_single_data_page+0xb65/0x1d60 fs/f2fs/data.c:2834
> > > > > > > > >      f2fs_write_cache_pages fs/f2fs/data.c:3133 [inline]
> > > > > > > > >      __f2fs_write_data_pages fs/f2fs/data.c:3288 [inline]
> > > > > > > > >      f2fs_write_data_pages+0x1efe/0x3a90 fs/f2fs/data.c:3315
> > > > > > > > >      do_writepages+0x35b/0x870 mm/page-writeback.c:2612
> > > > > > > > >      __writeback_single_inode+0x165/0x10b0 fs/fs-writeback.c:1650
> > > > > > > > >      writeback_sb_inodes+0x905/0x1260 fs/fs-writeback.c:1941
> > > > > > > > >      wb_writeback+0x457/0xce0 fs/fs-writeback.c:2117
> > > > > > > > >      wb_do_writeback fs/fs-writeback.c:2264 [inline]
> > > > > > > > >      wb_workfn+0x410/0x1090 fs/fs-writeback.c:2304
> > > > > > > > >      process_one_work kernel/workqueue.c:3254 [inline]
> > > > > > > > >      process_scheduled_works+0xa12/0x17c0 kernel/workqueue.c:3335
> > > > > > > > >      worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
> > > > > > > > >      kthread+0x2f2/0x390 kernel/kthread.c:388
> > > > > > > > >      ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
> > > > > > > > >      ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > > > > > > > > 
> > > > > > > > > The root cause is: inline_data inode can be fuzzed, so that there may
> > > > > > > > > be valid blkaddr in its direct node, once f2fs triggers background GC
> > > > > > > > > to migrate the block, it will hit f2fs_bug_on() during dirty page
> > > > > > > > > writeback.
> > > > > > > > > 
> > > > > > > > > Let's add sanity check on i_nid field for inline_data inode, meanwhile,
> > > > > > > > > forbid to migrate inline_data inode's data block to fix this issue.
> > > > > > > > > 
> > > > > > > > > Reported-by: syzbot+848062ba19c8782ca5c8@syzkaller.appspotmail.com
> > > > > > > > > Closes: https://lore.kernel.org/linux-f2fs-devel/000000000000d103ce06174d7ec3@google.com
> > > > > > > > > Signed-off-by: Chao Yu <chao@kernel.org>
> > > > > > > > > ---
> > > > > > > > >      fs/f2fs/f2fs.h   |  2 +-
> > > > > > > > >      fs/f2fs/gc.c     |  6 ++++++
> > > > > > > > >      fs/f2fs/inline.c | 17 ++++++++++++++++-
> > > > > > > > >      fs/f2fs/inode.c  |  2 +-
> > > > > > > > >      4 files changed, 24 insertions(+), 3 deletions(-)
> > > > > > > > > 
> > > > > > > > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > > > > > > > > index fced2b7652f4..c876813b5532 100644
> > > > > > > > > --- a/fs/f2fs/f2fs.h
> > > > > > > > > +++ b/fs/f2fs/f2fs.h
> > > > > > > > > @@ -4146,7 +4146,7 @@ extern struct kmem_cache *f2fs_inode_entry_slab;
> > > > > > > > >       * inline.c
> > > > > > > > >       */
> > > > > > > > >      bool f2fs_may_inline_data(struct inode *inode);
> > > > > > > > > -bool f2fs_sanity_check_inline_data(struct inode *inode);
> > > > > > > > > +bool f2fs_sanity_check_inline_data(struct inode *inode, struct page *ipage);
> > > > > > > > >      bool f2fs_may_inline_dentry(struct inode *inode);
> > > > > > > > >      void f2fs_do_read_inline_data(struct page *page, struct page *ipage);
> > > > > > > > >      void f2fs_truncate_inline_inode(struct inode *inode,
> > > > > > > > > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > > > > > > > > index e86c7f01539a..041957750478 100644
> > > > > > > > > --- a/fs/f2fs/gc.c
> > > > > > > > > +++ b/fs/f2fs/gc.c
> > > > > > > > > @@ -1563,6 +1563,12 @@ static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
> > > > > > > > >                                    continue;
> > > > > > > > >                            }
> > > > > > > > > +                 if (f2fs_has_inline_data(inode)) {
> > > > > > > > > +                         iput(inode);
> > > > > > > > > +                         set_sbi_flag(sbi, SBI_NEED_FSCK);
> > > > > > > > > +                         continue;
> > > > > > > > 
> > > > > > > > Any race condtion to get this as false alarm?
> > > > > > > 
> > > > > > > Since there is no reproducer for the bug, I doubt it was caused by metadata
> > > > > > > fuzzing, something like this:
> > > > > > > 
> > > > > > > - inline inode has one valid blkaddr in i_addr or in dnode reference by i_nid;
> > > > > > > - SIT/SSA entry of the block is valid;
> > > > > > > - background GC migrates the block;
> > > > > > > - kworker writeback it, and trigger the bug_on().
> > > > > > 
> > > > > > Wasn't detected by sanity_check_inode?
> > > > > 
> > > > > I fuzzed non-inline inode w/ below metadata fields:
> > > > > - i_blocks = 1
> > > > > - i_size = 2048
> > > > > - i_inline |= 0x02
> > > > > 
> > > > > sanity_check_inode() doesn't complain.
> > > > 
> > > > I mean, the below sanity_check_inode() can cover the fuzzed case? I'm wondering
> > > 
> > > I didn't figure out a generic way in sanity_check_inode() to catch all fuzzed cases.
> > 
> > 
> > The patch described:
> >   "The root cause is: inline_data inode can be fuzzed, so that there may
> >   be valid blkaddr in its direct node, once f2fs triggers background GC
> >   to migrate the block, it will hit f2fs_bug_on() during dirty page
> >   writeback."
> > 
> > Do you suspect the node block address was suddenly assigned after f2fs_iget()?
> 
> No, I suspect that the image was fuzzed by tools offline, not in runtime after
> mount().
> 
> > Otherwise, it looks checking them in sanity_check_inode would be enough.
> > 
> > > 
> > > e.g.
> > > case #1
> > > - blkaddr, its dnode, SSA and SIT are consistent
> > > - dnode.footer.ino points to inline inode
> > > - inline inode doesn't link to the donde
> > > 
> > > Something like fuzzed special file, please check details in below commit:
> > > 
> > > 9056d6489f5a ("f2fs: fix to do sanity check on inode type during garbage collection")
> > > 
> > > case #2
> > > - blkaddr, its dnode, SSA and SIT are consistent
> > > - blkaddr locates in inline inode's i_addr
> 
> The image status is something like above as I described.

Then, why not just checking the gc path only?

> 
> Thanks,
> 
> > > 
> > > Thanks,
> > > 
> > > > whether we really need to check it in the gc path.
> > > > 
> > > > > 
> > > > > Thanks,
> > > > > 
> > > > > > 
> > > > > > > 
> > > > > > > Thoughts?
> > > > > > > 
> > > > > > > Thanks,
> > > > > > > 
> > > > > > > > 
> > > > > > > > > +                 }
> > > > > > > > > +
> > > > > > > > >                            err = f2fs_gc_pinned_control(inode, gc_type, segno);
> > > > > > > > >                            if (err == -EAGAIN) {
> > > > > > > > >                                    iput(inode);
> > > > > > > > > diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
> > > > > > > > > index ac00423f117b..067600fed3d4 100644
> > > > > > > > > --- a/fs/f2fs/inline.c
> > > > > > > > > +++ b/fs/f2fs/inline.c
> > > > > > > > > @@ -33,11 +33,26 @@ bool f2fs_may_inline_data(struct inode *inode)
> > > > > > > > >            return !f2fs_post_read_required(inode);
> > > > > > > > >      }
> > > > > > > > > -bool f2fs_sanity_check_inline_data(struct inode *inode)
> > > > > > > > > +static bool has_node_blocks(struct inode *inode, struct page *ipage)
> > > > > > > > > +{
> > > > > > > > > + struct f2fs_inode *ri = F2FS_INODE(ipage);
> > > > > > > > > + int i;
> > > > > > > > > +
> > > > > > > > > + for (i = 0; i < DEF_NIDS_PER_INODE; i++) {
> > > > > > > > > +         if (ri->i_nid[i])
> > > > > > > > > +                 return true;
> > > > > > > > > + }
> > > > > > > > > + return false;
> > > > > > > > > +}
> > > > > > > > > +
> > > > > > > > > +bool f2fs_sanity_check_inline_data(struct inode *inode, struct page *ipage)
> > > > > > > > >      {
> > > > > > > > >            if (!f2fs_has_inline_data(inode))
> > > > > > > > >                    return false;
> > > > > > > > > + if (has_node_blocks(inode, ipage))
> > > > > > > > > +         return false;
> > > > > > > > > +
> > > > > > > > >            if (!support_inline_data(inode))
> > > > > > > > >                    return true;
> > > > > > > > > diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> > > > > > > > > index c26effdce9aa..1423cd27a477 100644
> > > > > > > > > --- a/fs/f2fs/inode.c
> > > > > > > > > +++ b/fs/f2fs/inode.c
> > > > > > > > > @@ -343,7 +343,7 @@ static bool sanity_check_inode(struct inode *inode, struct page *node_page)
> > > > > > > > >                    }
> > > > > > > > >            }
> > > > > > > > > - if (f2fs_sanity_check_inline_data(inode)) {
> > > > > > > > > + if (f2fs_sanity_check_inline_data(inode, node_page)) {
> > > > > > > > >                    f2fs_warn(sbi, "%s: inode (ino=%lx, mode=%u) should not have inline_data, run fsck to fix",
> > > > > > > > >                              __func__, inode->i_ino, inode->i_mode);
> > > > > > > > >                    return false;
> > > > > > > > > --
> > > > > > > > > 2.40.1