Re: f2fs: BUG_ON() is triggered when mount valid f2fs filesystem

[Jaegeuk Kim <jaegeuk.kim@samsung.com>]

Hi,

2014-04-16 (수), 18:11 -0700, Alexey Khoroshilov:
> Hi,
> 
> But would not ability to trigger BUG_ON by mounting a crafted image
> considered as an issue having security implications?

Sorry, I can't come up with you.
Could you please explain why this can be related to the security hole?
Did you mean it needs to avoid such the BUG_ONs if the image has
obsolete data being used before?

Thanks,

> 
> Regards,
> Alexey
> 
> 
> On 16.04.2014 16:35, Jaegeuk Kim wrote:
> > Hi,
> >
> > 2014-04-16 (수), 13:11 +0400, Andrey Tsyvarev:
> >> Hi,
> >>
> >> With this patch mounting of the image continues to fail (with similar 
> >> BUG_ON).
> >> But when image is formatted again (and steps mentioned in the previous 
> >> message are performed),
> >> mounting of it is now succeed.
> >>
> >> Is this is a true purpose of the patch?
> > Indeed. The patch solves there-in root cause.
> > But, if you're trying to use the failed image again, simply you can skip
> > the errorneous part by:
> >
> > # mount ... -o disable_roll_forward ...
> >
> > Once sync or umount whatever checkpoint is done after that, the image
> > will be mounted without "disable_roll_forward".
> >
> > Thanks,
> >
> >> 15.04.2014 15:04, Jaegeuk Kim пишет:
> >>> Hi,
> >>>
> >>> Thank you for the report.
> >>> I retrieved the fault image and found out that previous garbage data
> >>> wreak such the wrong behaviors.
> >>> So, I wrote the following patch that fills one zero-block at the
> >>> checkpoint procedure.
> >>> If the underlying device supports discard, I expect that it mostly
> >>> doesn't incur any performance regression significantly.
> >>>
> >>> Could you test this patch?
> >>>
> >>> >From 60588ceb7277aae2a79e7f67f5217d1256720d78 Mon Sep 17 00:00:00 2001
> >>> From: Jaegeuk Kim <jaegeuk.kim@samsung.com>
> >>> Date: Tue, 15 Apr 2014 13:57:55 +0900
> >>> Subject: [PATCH] f2fs: avoid to conduct roll-forward due to the remained
> >>>   garbage blocks
> >>>
> >>> The f2fs always scans the next chain of direct node blocks.
> >>> But some garbage blocks are able to be remained due to no discard
> >>> support or
> >>> SSR triggers.
> >>> This occasionally wreaks recovering wrong inodes that were used or
> >>> BUG_ONs
> >>> due to reallocating node ids as follows.
> >>>
> >>> When mount this f2fs image:
> >>> http://linuxtesting.org/downloads/f2fs_fault_image.zip
> >>> BUG_ON is triggered in f2fs driver (messages below are generated on
> >>> kernel 3.13.2; for other kernels output is similar):
> >>>
> >>> kernel BUG at fs/f2fs/node.c:215!
> >>>   Call Trace:
> >>>   [<ffffffffa032ebad>] recover_inode_page+0x1fd/0x3e0 [f2fs]
> >>>   [<ffffffff811446e7>] ? __lock_page+0x67/0x70
> >>>   [<ffffffff81089990>] ? autoremove_wake_function+0x50/0x50
> >>>   [<ffffffffa0337788>] recover_fsync_data+0x1398/0x15d0 [f2fs]
> >>>   [<ffffffff812b9e5c>] ? selinux_d_instantiate+0x1c/0x20
> >>>   [<ffffffff811cb20b>] ? d_instantiate+0x5b/0x80
> >>>   [<ffffffffa0321044>] f2fs_fill_super+0xb04/0xbf0 [f2fs]
> >>>   [<ffffffff811b861e>] ? mount_bdev+0x7e/0x210
> >>>   [<ffffffff811b8769>] mount_bdev+0x1c9/0x210
> >>>   [<ffffffffa0320540>] ? validate_superblock+0x210/0x210 [f2fs]
> >>>   [<ffffffffa031cf8d>] f2fs_mount+0x1d/0x30 [f2fs]
> >>>   [<ffffffff811b9497>] mount_fs+0x47/0x1c0
> >>>   [<ffffffff81166e00>] ? __alloc_percpu+0x10/0x20
> >>>   [<ffffffff811d4032>] vfs_kern_mount+0x72/0x110
> >>>   [<ffffffff811d6763>] do_mount+0x493/0x910
> >>>   [<ffffffff811615cb>] ? strndup_user+0x5b/0x80
> >>>   [<ffffffff811d6c70>] SyS_mount+0x90/0xe0
> >>>   [<ffffffff8166f8d9>] system_call_fastpath+0x16/0x1b
> >>>
> >>> Found by Linux File System Verification project (linuxtesting.org).
> >>>
> >>> Reported-by: Andrey Tsyvarev <tsyvarev@ispras.ru>
> >>> Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
> >>> ---
> >>>   fs/f2fs/checkpoint.c |  6 ++++++
> >>>   fs/f2fs/f2fs.h       |  1 +
> >>>   fs/f2fs/segment.c    | 17 +++++++++++++++--
> >>>   3 files changed, 22 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> >>> index 4aa521a..890e23d 100644
> >>> --- a/fs/f2fs/checkpoint.c
> >>> +++ b/fs/f2fs/checkpoint.c
> >>> @@ -762,6 +762,12 @@ static void do_checkpoint(struct f2fs_sb_info *sbi,
> >>> bool is_umount)
> >>>   	void *kaddr;
> >>>   	int i;
> >>>   
> >>> +	/*
> >>> +	 * This avoids to conduct wrong roll-forward operations and uses
> >>> +	 * metapages, so should be called prior to sync_meta_pages below.
> >>> +	 */
> >>> +	discard_next_dnode(sbi);
> >>> +
> >>>   	/* Flush all the NAT/SIT pages */
> >>>   	while (get_pages(sbi, F2FS_DIRTY_META))
> >>>   		sync_meta_pages(sbi, META, LONG_MAX);
> >>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> >>> index 2ecac83..2c5a5da 100644
> >>> --- a/fs/f2fs/f2fs.h
> >>> +++ b/fs/f2fs/f2fs.h
> >>> @@ -1179,6 +1179,7 @@ int f2fs_issue_flush(struct f2fs_sb_info *);
> >>>   void invalidate_blocks(struct f2fs_sb_info *, block_t);
> >>>   void refresh_sit_entry(struct f2fs_sb_info *, block_t, block_t);
> >>>   void clear_prefree_segments(struct f2fs_sb_info *);
> >>> +void discard_next_dnode(struct f2fs_sb_info *);
> >>>   int npages_for_summary_flush(struct f2fs_sb_info *);
> >>>   void allocate_new_segments(struct f2fs_sb_info *);
> >>>   struct page *get_sum_page(struct f2fs_sb_info *, unsigned int);
> >>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> >>> index 1e264e7..9993f94 100644
> >>> --- a/fs/f2fs/segment.c
> >>> +++ b/fs/f2fs/segment.c
> >>> @@ -335,13 +335,26 @@ static void locate_dirty_segment(struct
> >>> f2fs_sb_info *sbi, unsigned int segno)
> >>>   	mutex_unlock(&dirty_i->seglist_lock);
> >>>   }
> >>>   
> >>> -static void f2fs_issue_discard(struct f2fs_sb_info *sbi,
> >>> +static int f2fs_issue_discard(struct f2fs_sb_info *sbi,
> >>>   				block_t blkstart, block_t blklen)
> >>>   {
> >>>   	sector_t start = SECTOR_FROM_BLOCK(sbi, blkstart);
> >>>   	sector_t len = SECTOR_FROM_BLOCK(sbi, blklen);
> >>> -	blkdev_issue_discard(sbi->sb->s_bdev, start, len, GFP_NOFS, 0);
> >>>   	trace_f2fs_issue_discard(sbi->sb, blkstart, blklen);
> >>> +	return blkdev_issue_discard(sbi->sb->s_bdev, start, len, GFP_NOFS, 0);
> >>> +}
> >>> +
> >>> +void discard_next_dnode(struct f2fs_sb_info *sbi)
> >>> +{
> >>> +	struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_WARM_NODE);
> >>> +	block_t blkaddr = NEXT_FREE_BLKADDR(sbi, curseg);
> >>> +
> >>> +	if (f2fs_issue_discard(sbi, blkaddr, 1)) {
> >>> +		struct page *page = grab_meta_page(sbi, blkaddr);
> >>> +		/* zero-filled page */
> >>> +		set_page_dirty(page);
> >>> +		f2fs_put_page(page, 1);
> >>> +	}
> >>>   }
> >>>   
> >>>   static void add_discard_addrs(struct f2fs_sb_info *sbi,
> 
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-- 
Jaegeuk Kim
Samsung