On 2018/8/31 at 下午3:02, Chao Yu wrote:
> On 2018/8/31 0:19, cgxu519 wrote:
> >
> > On 08/30/2018 11:41 PM, Chao Yu wrote:
> >> Hi Chengguang,
> >>
> >> On 2018/8/30 21:33, Chengguang Xu wrote:
> >>> Add additinal sanity check for irregular case(e.g. corruption).
> >>> If size of extended attribution is smaller than size of acl header,
> >>> then return -EINVAL.
> >>>
> >>> Signed-off-by: Chengguang Xu <cgxu...@gmx.com>
> >>> ---
> >>> fs/f2fs/acl.c | 3 +++
> >>> 1 file changed, 3 insertions(+)
> >>>
> >>> diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
> >>> index 111824199a88..79e9ea773070 100644
> >>> --- a/fs/f2fs/acl.c
> >>> +++ b/fs/f2fs/acl.c
> >>> @@ -53,6 +53,9 @@ static struct posix_acl *f2fs_acl_from_disk(const char
> >>> *value, size_t size)
> >>> struct f2fs_acl_entry *entry = (struct f2fs_acl_entry *)(hdr +
> >>> 1);
> >>> const char *end = value + size;
> >>>
> >>> + if (size < sizeof(f2fs_acl_header))
> >>> + return ERR_PTR(-EINVAL);
> >> I guess below codes have checked that already?
> >>
> >> count = f2fs_acl_count(size);
> >> if (count < 0)
> >> return ERR_PTR(-EINVAL);
> >
> > Hi Chao,
> >
> > Thanks for prompt reply.
> >
> > I still think in a rare case, it can pass the check in f2fs_acl_count()
> > and cause unexpected behavior.
> >
> > For example, like below code path in f2fs_acl_count().
>
> if size < sizeof(f2fs_acl_header)
>
> size -= sizeof(struct f2fs_acl_header);
>
> size should be smaller than zero, right?
>
> >
> > -> if (s < 0) {
> > if (size % sizeof(struct f2fs_acl_entry_short))
> > return -1;
> > -> return size / sizeof(struct f2fs_acl_entry_short);
>
> So the return value should be smaller than zero?
size is unsigned so the return value will not be negative here.
Thanks,
Chengguang
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