On Tue, May 17, 2022 at 11:10:15PM +0800, Chao Yu wrote:
> On 2022/5/12 19:58, Gao Xiang wrote:
> > I got some KASAN report as below:
> >
> > [ 46.959738]
> > ==================================================================
> > [ 46.960430] BUG: KASAN: use-after-free in
> > z_erofs_shifted_transform+0x2bd/0x370
> > [ 46.960430] Read of size 4074 at addr ffff8880300c2f8e by task fssum/188
> > ...
> > [ 46.960430] Call Trace:
> > [ 46.960430] <TASK>
> > [ 46.960430] dump_stack_lvl+0x41/0x5e
> > [ 46.960430] print_report.cold+0xb2/0x6b7
> > [ 46.960430] ? z_erofs_shifted_transform+0x2bd/0x370
> > [ 46.960430] kasan_report+0x8a/0x140
> > [ 46.960430] ? z_erofs_shifted_transform+0x2bd/0x370
> > [ 46.960430] kasan_check_range+0x14d/0x1d0
> > [ 46.960430] memcpy+0x20/0x60
> > [ 46.960430] z_erofs_shifted_transform+0x2bd/0x370
> > [ 46.960430] z_erofs_decompress_pcluster+0xaae/0x1080
> >
> > The root cause is that the tail pcluster won't be a complete filesystem
> > block anymore. So if ztailpacking is used, the second part of an
> > uncompresed tail pcluster may not be ``rq->pageofs_out``.
>
> uncompressed
Fixed, thanks!
Thanks,
Gao Xiang
>
> >
> > Fixes: ab749badf9f4 ("erofs: support unaligned data decompression")
> > Fixes: cecf864d3d76 ("erofs: support inline data decompression")
> > Signed-off-by: Gao Xiang <[email protected]>
>
> Reviewed-by: Chao Yu <[email protected]>
>
> Thanks,
>
> > ---
> > fs/erofs/decompressor.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> > index 0f445f7e1df8..6dca1900c733 100644
> > --- a/fs/erofs/decompressor.c
> > +++ b/fs/erofs/decompressor.c
> > @@ -320,6 +320,7 @@ static int z_erofs_shifted_transform(struct
> > z_erofs_decompress_req *rq,
> > PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
> > const unsigned int righthalf = min_t(unsigned int, rq->outputsize,
> > PAGE_SIZE - rq->pageofs_out);
> > + const unsigned int lefthalf = rq->outputsize - righthalf;
> > unsigned char *src, *dst;
> > if (nrpages_out > 2) {
> > @@ -342,10 +343,10 @@ static int z_erofs_shifted_transform(struct
> > z_erofs_decompress_req *rq,
> > if (nrpages_out == 2) {
> > DBG_BUGON(!rq->out[1]);
> > if (rq->out[1] == *rq->in) {
> > - memmove(src, src + righthalf, rq->pageofs_out);
> > + memmove(src, src + righthalf, lefthalf);
> > } else {
> > dst = kmap_atomic(rq->out[1]);
> > - memcpy(dst, src + righthalf, rq->pageofs_out);
> > + memcpy(dst, src + righthalf, lefthalf);
> > kunmap_atomic(dst);
> > }
> > }
