On 10.07.19 г. 11:02 ч., Qu Wenruo wrote: > Although we have start, len check for extent buffer reader/write (e.g. > read_extent_buffer()), those checks has its limitations: > - No overflow check > Values like start = 1024 len = -1024 can still pass the basic > (start + len) > eb->len check. > > - Checks are not consistent > For read_extent_buffer() we only check (start + len) against eb->len. > While for memcmp_extent_buffer() we also check start against eb->len. > > - Different error reporting mechanism > We use WARN() in read_extent_buffer() but BUG() in > memcpy_extent_buffer(). > > - Still modify memory if the request is obviously wrong > In read_extent_buffer() even we find (start + len) > eb->len, we still > call memset(dst, 0, len), which can eaisly cause memory access error > if start + len overflows. > > To address above problems, this patch creates a new common function to > check such access, check_eb_range(). > - Add overflow check > This function checks start, start + len against eb->len and overflow > check. > > - Unified checks > > - Unified error reports > Will call WARN() if CONFIG_BTRFS_DEBUG is configured. > And also do btrfs_warn() message for non-debug build. > > - Exit ASAP if check fails > No more possible memory corruption. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202817 > [ Inspired by above report, the report itself is already addressed ] > Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> > --- > fs/btrfs/extent_io.c | 79 +++++++++++++++++++++++--------------------- > 1 file changed, 42 insertions(+), 37 deletions(-) > > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c > index db337e53aab3..b072ef5bceac 100644 > --- a/fs/btrfs/extent_io.c > +++ b/fs/btrfs/extent_io.c > @@ -5429,6 +5429,31 @@ int read_extent_buffer_pages(struct extent_buffer *eb, int wait, int mirror_num) > return ret; > } > > +/* > + * Check if the [start, start + len) range is valid before reading/writing > + * the eb. > + * > + * Caller should not touch the dst/src memory if this function returns error. > + */ > +static int check_eb_range(const struct extent_buffer *eb, unsigned long start, > + unsigned long len) > +{ > + unsigned long end; > + > + /* start, start + len should not go beyond eb->len nor overflow */ > + if (unlikely(start > eb->len || start + len > eb->len || I think your check here is wrong, it should be start + len > start + eb->len. start is the logical address hence it can be a lot bigger than the size of the eb which is 16k by default. > + check_add_overflow(start, len, &end))) { > + WARN(IS_ENABLED(CONFIG_BTRFS_DEBUG), KERN_ERR > +"btrfs: bad eb rw request, eb bytenr=%llu len=%lu rw start=%lu len=%lu\n", > + eb->start, eb->len, start, len); > + btrfs_warn(eb->fs_info, > +"btrfs: bad eb rw request, eb bytenr=%llu len=%lu rw start=%lu len=%lu\n", > + eb->start, eb->len, start, len); If CONFIG_BTRFS_DEBUG is enabled then we will print the warning text twice. Simply make it: WARN_ON(IS_ENABLED()) and leave the btrfs_Warn to always print the text. > + return -EINVAL; > + } > + return 0; > +} > + > void read_extent_buffer(const struct extent_buffer *eb, void *dstv, > unsigned long start, unsigned long len) > { > @@ -5440,12 +5465,8 @@ void read_extent_buffer(const struct extent_buffer *eb, void *dstv, > size_t start_offset = offset_in_page(eb->start); > unsigned long i = (start_offset + start) >> PAGE_SHIFT; > > - if (start + len > eb->len) { > - WARN(1, KERN_ERR "btrfs bad mapping eb start %llu len %lu, wanted %lu %lu\n", > - eb->start, eb->len, start, len); > - memset(dst, 0, len); > + if (check_eb_range(eb, start, len)) > return; > - } > > offset = offset_in_page(start_offset + start); > > @@ -5554,8 +5575,8 @@ int memcmp_extent_buffer(const struct extent_buffer *eb, const void *ptrv, > unsigned long i = (start_offset + start) >> PAGE_SHIFT; > int ret = 0; > > - WARN_ON(start > eb->len); > - WARN_ON(start + len > eb->start + eb->len); > + if (check_eb_range(eb, start, len)) > + return -EINVAL; > > offset = offset_in_page(start_offset + start); > > @@ -5609,8 +5630,8 @@ void write_extent_buffer(struct extent_buffer *eb, const void *srcv, > size_t start_offset = offset_in_page(eb->start); > unsigned long i = (start_offset + start) >> PAGE_SHIFT; > > - WARN_ON(start > eb->len); > - WARN_ON(start + len > eb->start + eb->len); > + if (check_eb_range(eb, start, len)) > + return; > > offset = offset_in_page(start_offset + start); > > @@ -5639,8 +5660,8 @@ void memzero_extent_buffer(struct extent_buffer *eb, unsigned long start, > size_t start_offset = offset_in_page(eb->start); > unsigned long i = (start_offset + start) >> PAGE_SHIFT; > > - WARN_ON(start > eb->len); > - WARN_ON(start + len > eb->start + eb->len); > + if (check_eb_range(eb, start, len)) > + return; > > offset = offset_in_page(start_offset + start); > > @@ -5684,6 +5705,10 @@ void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src, > size_t start_offset = offset_in_page(dst->start); > unsigned long i = (start_offset + dst_offset) >> PAGE_SHIFT; > > + if (check_eb_range(dst, dst_offset, len) || > + check_eb_range(src, src_offset, len)) > + return; > + > WARN_ON(src->len != dst_len); > > offset = offset_in_page(start_offset + dst_offset); > @@ -5872,7 +5897,6 @@ static void copy_pages(struct page *dst_page, struct page *src_page, > void memcpy_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset, > unsigned long src_offset, unsigned long len) > { > - struct btrfs_fs_info *fs_info = dst->fs_info; > size_t cur; > size_t dst_off_in_page; > size_t src_off_in_page; > @@ -5880,18 +5904,9 @@ void memcpy_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset, > unsigned long dst_i; > unsigned long src_i; > > - if (src_offset + len > dst->len) { > - btrfs_err(fs_info, > - "memmove bogus src_offset %lu move len %lu dst len %lu", > - src_offset, len, dst->len); > - BUG(); > - } > - if (dst_offset + len > dst->len) { > - btrfs_err(fs_info, > - "memmove bogus dst_offset %lu move len %lu dst len %lu", > - dst_offset, len, dst->len); > - BUG(); > - } > + if (check_eb_range(dst, dst_offset, len) || > + check_eb_range(dst, src_offset, len)) > + return; > > while (len > 0) { > dst_off_in_page = offset_in_page(start_offset + dst_offset); > @@ -5917,7 +5932,6 @@ void memcpy_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset, > void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset, > unsigned long src_offset, unsigned long len) > { > - struct btrfs_fs_info *fs_info = dst->fs_info; > size_t cur; > size_t dst_off_in_page; > size_t src_off_in_page; > @@ -5927,18 +5941,9 @@ void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset, > unsigned long dst_i; > unsigned long src_i; > > - if (src_offset + len > dst->len) { > - btrfs_err(fs_info, > - "memmove bogus src_offset %lu move len %lu len %lu", > - src_offset, len, dst->len); > - BUG(); > - } > - if (dst_offset + len > dst->len) { > - btrfs_err(fs_info, > - "memmove bogus dst_offset %lu move len %lu len %lu", > - dst_offset, len, dst->len); > - BUG(); > - } > + if (check_eb_range(dst, dst_offset, len) || > + check_eb_range(dst, src_offset, len)) > + return; > if (dst_offset < src_offset) { > memcpy_extent_buffer(dst, dst_offset, src_offset, len); > return; >
