Messages in this thread | | | Subject | Re: [f2fs-dev] [PATCH 3/4] f2fs: fix NULL pointer dereference in f2fs_verity_work() | From | Chao Yu <> | Date | Sat, 21 Mar 2020 20:16:52 +0800 |
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On 2020-3-21 3:11, Eric Biggers wrote: > On Thu, Mar 19, 2020 at 07:57:59PM +0800, Chao Yu wrote: >> If both compression and fsverity feature is on, generic/572 will >> report below NULL pointer dereference bug. >> >> BUG: kernel NULL pointer dereference, address: 0000000000000018 >> RIP: 0010:f2fs_verity_work+0x60/0x90 [f2fs] >> #PF: supervisor read access in kernel mode >> Workqueue: fsverity_read_queue f2fs_verity_work [f2fs] >> RIP: 0010:f2fs_verity_work+0x60/0x90 [f2fs] >> Call Trace: >> process_one_work+0x16c/0x3f0 >> worker_thread+0x4c/0x440 >> ? rescuer_thread+0x350/0x350 >> kthread+0xf8/0x130 >> ? kthread_unpark+0x70/0x70 >> ret_from_fork+0x35/0x40 >> >> There are two issue in f2fs_verity_work(): >> - it needs to traverse and verify all pages in bio. >> - if pages in bio belong to non-compressed cluster, accessing >> decompress IO context stored in page private will cause NULL >> pointer dereference. >> >> Fix them. >> >> Signed-off-by: Chao Yu <yuchao0@huawei.com> >> --- >> fs/f2fs/data.c | 35 ++++++++++++++++++++++++++++++----- >> 1 file changed, 30 insertions(+), 5 deletions(-) >> >> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c >> index 5c5db09324b7..66e49fc1056e 100644 >> --- a/fs/f2fs/data.c >> +++ b/fs/f2fs/data.c >> @@ -187,12 +187,37 @@ static void f2fs_verify_pages(struct page **rpages, unsigned int cluster_size) >> >> static void f2fs_verify_bio(struct bio *bio) >> { >> - struct page *page = bio_first_page_all(bio); >> - struct decompress_io_ctx *dic = >> - (struct decompress_io_ctx *)page_private(page); >> + struct bio_vec *bv; >> + struct bvec_iter_all iter_all; >> + struct decompress_io_ctx *dic, *pdic = NULL; >> + >> + bio_for_each_segment_all(bv, bio, iter_all) { >> + struct page *page = bv->bv_page; >> + >> + dic = (struct decompress_io_ctx *)page_private(page); >> + >> + if (dic) { >> + if (dic != pdic) { >> + f2fs_verify_pages(dic->rpages, >> + dic->cluster_size); >> + f2fs_free_dic(dic); >> + pdic = dic; >> + } >> + continue; >> + } >> + pdic = dic; >> >> - f2fs_verify_pages(dic->rpages, dic->cluster_size); >> - f2fs_free_dic(dic); >> + if (bio->bi_status || PageError(page)) { >> + ClearPageUptodate(page); >> + ClearPageError(page); >> + } else { >> + if (fsverity_verify_page(page)) >> + SetPageUptodate(page); >> + else >> + SetPageError(page); >> + } >> + unlock_page(page); >> + } > > I'm a bit confused why you added SetPageError() before unlocking the page. > The other error paths actually clear the Error flag, not set it. I thought > there's a reason for that?
These codes were copy&paste from f2fs_decompress_end_io(), I guess I missed to check that logic, so anyway, we need another patch to fix that first.
Thanks for pointing out this.
Thanks,
> > - Eric > > > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel >
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