Re: [PATCH 5.10 60/76] f2fs: fix to do sanity check on last xattr entry in __f2fs_setxattr()

[Chao Yu]

On 2022/1/4 5:11, Salvatore Bonaccorso wrote:
> Hi,
>
> On Mon, Dec 27, 2021 at 04:31:15PM +0100, Greg Kroah-Hartman wrote:
> > From: Chao Yu <chao@xxxxxxxxxx>
> >
> > commit 5598b24efaf4892741c798b425d543e4bed357a1 upstream.

I've no idea.

I didn't add this line from v1 to v3:

https://lore.kernel.org/lkml/20211211154059.7173-1-chao@xxxxxxxxxx/T/
https://lore.kernel.org/all/20211212071923.2398-1-chao@xxxxxxxxxx/T/
https://lore.kernel.org/all/20211212091630.6325-1-chao@xxxxxxxxxx/T/

Am I missing anything?

Thanks,

> > As Wenqing Liu reported in bugzilla:
> >
> > https://bugzilla.kernel.org/show_bug.cgi?id=215235
> >
> > - Overview
> > page fault in f2fs_setxattr() when mount and operate on corrupted image
> >
> > - Reproduce
> > tested on kernel 5.16-rc3, 5.15.X under root
> >
> > 1. unzip tmp7.zip
> > 2. ./single.sh f2fs 7
> >
> > Sometimes need to run the script several times
> >
> > - Kernel dump
> > loop0: detected capacity change from 0 to 131072
> > F2FS-fs (loop0): Found nat_bits in checkpoint
> > F2FS-fs (loop0): Mounted with checkpoint version = 7548c2ee
> > BUG: unable to handle page fault for address: ffffe47bc7123f48
> > RIP: 0010:kfree+0x66/0x320
> > Call Trace:
> >   __f2fs_setxattr+0x2aa/0xc00 [f2fs]
> >   f2fs_setxattr+0xfa/0x480 [f2fs]
> >   __f2fs_set_acl+0x19b/0x330 [f2fs]
> >   __vfs_removexattr+0x52/0x70
> >   __vfs_removexattr_locked+0xb1/0x140
> >   vfs_removexattr+0x56/0x100
> >   removexattr+0x57/0x80
> >   path_removexattr+0xa3/0xc0
> >   __x64_sys_removexattr+0x17/0x20
> >   do_syscall_64+0x37/0xb0
> >   entry_SYSCALL_64_after_hwframe+0x44/0xae
> >
> > The root cause is in __f2fs_setxattr(), we missed to do sanity check on
> > last xattr entry, result in out-of-bound memory access during updating
> > inconsistent xattr data of target inode.
> >
> > After the fix, it can detect such xattr inconsistency as below:
> >
> > F2FS-fs (loop11): inode (7) has invalid last xattr entry, entry_size: 60676
> > F2FS-fs (loop11): inode (8) has corrupted xattr
> > F2FS-fs (loop11): inode (8) has corrupted xattr
> > F2FS-fs (loop11): inode (8) has invalid last xattr entry, entry_size: 47736
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Reported-by: Wenqing Liu <wenqingliu0120@xxxxxxxxx>
> > Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
> > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > ---
> >   fs/f2fs/xattr.c |   11 ++++++++++-
> >   1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > --- a/fs/f2fs/xattr.c
> > +++ b/fs/f2fs/xattr.c
> > @@ -680,8 +680,17 @@ static int __f2fs_setxattr(struct inode
> >   	}
> >   
> >   	last = here;
> > -	while (!IS_XATTR_LAST_ENTRY(last))
> > +	while (!IS_XATTR_LAST_ENTRY(last)) {
> > +		if ((void *)(last) + sizeof(__u32) > last_base_addr ||
> > +			(void *)XATTR_NEXT_ENTRY(last) > last_base_addr) {
> > +			f2fs_err(F2FS_I_SB(inode), "inode (%lu) has invalid last xattr entry, entry_size: %zu",
> > +					inode->i_ino, ENTRY_SIZE(last));
> > +			set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK);
> > +			error = -EFSCORRUPTED;
> > +			goto exit;
> > +		}
> >   		last = XATTR_NEXT_ENTRY(last);
> > +	}
> >   
> >   	newsize = XATTR_ALIGN(sizeof(struct f2fs_xattr_entry) + len + size);
>
> It looks this commit while it was applied to several stable series
> (TTBOMK in 5.15.12, 5.10.89, 5.4.169, 4.19.223 and 4.14.260) it is
> still missing from mainline, Chao, or anyone else, do you know what
> happened here?
>
> Regards,
> Salvatore