The patch below does not apply to the 5.0-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From af692e117cb8cd9d3d844d413095775abc1217f9 Mon Sep 17 00:00:00 2001
From: Gao Xiang gaoxiang25@huawei.com Date: Wed, 27 Feb 2019 13:33:30 +0800 Subject: [PATCH] staging: erofs: compressed_pages should not be accessed again after freed
This patch resolves the following page use-after-free issue, z_erofs_vle_unzip: ... for (i = 0; i < nr_pages; ++i) { ... z_erofs_onlinepage_endio(page); (1) }
for (i = 0; i < clusterpages; ++i) { page = compressed_pages[i];
if (page->mapping == mngda) (2) continue; /* recycle all individual staging pages */ (void)z_erofs_gather_if_stagingpage(page_pool, page); (3) WRITE_ONCE(compressed_pages[i], NULL); } ...
After (1) is executed, page is freed and could be then reused, if compressed_pages is scanned after that, it could fall info (2) or (3) by mistake and that could finally be in a mess.
This patch aims to solve the above issue only with little changes as much as possible in order to make the fix backport easier.
Fixes: 3883a79abd02 ("staging: erofs: introduce VLE decompression support") Cc: stable@vger.kernel.org # 4.19+ Signed-off-by: Gao Xiang gaoxiang25@huawei.com Reviewed-by: Chao Yu yuchao0@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c index a127d8db76d8..416dde4e8ea1 100644 --- a/drivers/staging/erofs/unzip_vle.c +++ b/drivers/staging/erofs/unzip_vle.c @@ -986,11 +986,10 @@ static int z_erofs_vle_unzip(struct super_block *sb, if (llen > grp->llen) llen = grp->llen;
- err = z_erofs_vle_unzip_fast_percpu(compressed_pages, - clusterpages, pages, llen, work->pageofs, - z_erofs_onlinepage_endio); + err = z_erofs_vle_unzip_fast_percpu(compressed_pages, clusterpages, + pages, llen, work->pageofs); if (err != -ENOTSUPP) - goto out_percpu; + goto out;
if (sparsemem_pages >= nr_pages) goto skip_allocpage; @@ -1011,8 +1010,25 @@ static int z_erofs_vle_unzip(struct super_block *sb, erofs_vunmap(vout, nr_pages);
out: + /* must handle all compressed pages before endding pages */ + for (i = 0; i < clusterpages; ++i) { + page = compressed_pages[i]; + +#ifdef EROFS_FS_HAS_MANAGED_CACHE + if (page->mapping == MNGD_MAPPING(sbi)) + continue; +#endif + /* recycle all individual staging pages */ + (void)z_erofs_gather_if_stagingpage(page_pool, page); + + WRITE_ONCE(compressed_pages[i], NULL); + } + for (i = 0; i < nr_pages; ++i) { page = pages[i]; + if (!page) + continue; + DBG_BUGON(!page->mapping);
/* recycle all individual staging pages */ @@ -1025,20 +1041,6 @@ static int z_erofs_vle_unzip(struct super_block *sb, z_erofs_onlinepage_endio(page); }
-out_percpu: - for (i = 0; i < clusterpages; ++i) { - page = compressed_pages[i]; - -#ifdef EROFS_FS_HAS_MANAGED_CACHE - if (page->mapping == MNGD_MAPPING(sbi)) - continue; -#endif - /* recycle all individual staging pages */ - (void)z_erofs_gather_if_stagingpage(page_pool, page); - - WRITE_ONCE(compressed_pages[i], NULL); - } - if (pages == z_pagemap_global) mutex_unlock(&z_pagemap_global_lock); else if (unlikely(pages != pages_onstack)) diff --git a/drivers/staging/erofs/unzip_vle.h b/drivers/staging/erofs/unzip_vle.h index 9dafa8dc712c..517e5ce8c5e9 100644 --- a/drivers/staging/erofs/unzip_vle.h +++ b/drivers/staging/erofs/unzip_vle.h @@ -218,8 +218,7 @@ int z_erofs_vle_plain_copy(struct page **compressed_pages, int z_erofs_vle_unzip_fast_percpu(struct page **compressed_pages, unsigned int clusterpages, struct page **pages, unsigned int outlen, - unsigned short pageofs, - void (*endio)(struct page *)); + unsigned short pageofs); int z_erofs_vle_unzip_vmap(struct page **compressed_pages, unsigned int clusterpages, void *vaddr, unsigned int llen, diff --git a/drivers/staging/erofs/unzip_vle_lz4.c b/drivers/staging/erofs/unzip_vle_lz4.c index 8e8d705a6861..48b263a2731a 100644 --- a/drivers/staging/erofs/unzip_vle_lz4.c +++ b/drivers/staging/erofs/unzip_vle_lz4.c @@ -125,8 +125,7 @@ int z_erofs_vle_unzip_fast_percpu(struct page **compressed_pages, unsigned int clusterpages, struct page **pages, unsigned int outlen, - unsigned short pageofs, - void (*endio)(struct page *)) + unsigned short pageofs) { void *vin, *vout; unsigned int nr_pages, i, j; @@ -148,19 +147,16 @@ int z_erofs_vle_unzip_fast_percpu(struct page **compressed_pages, ret = z_erofs_unzip_lz4(vin, vout + pageofs, clusterpages * PAGE_SIZE, outlen);
- if (ret >= 0) { - outlen = ret; - ret = 0; - } + if (ret < 0) + goto out; + ret = 0;
for (i = 0; i < nr_pages; ++i) { j = min((unsigned int)PAGE_SIZE - pageofs, outlen);
if (pages[i]) { - if (ret < 0) { - SetPageError(pages[i]); - } else if (clusterpages == 1 && - pages[i] == compressed_pages[0]) { + if (clusterpages == 1 && + pages[i] == compressed_pages[0]) { memcpy(vin + pageofs, vout + pageofs, j); } else { void *dst = kmap_atomic(pages[i]); @@ -168,12 +164,13 @@ int z_erofs_vle_unzip_fast_percpu(struct page **compressed_pages, memcpy(dst + pageofs, vout + pageofs, j); kunmap_atomic(dst); } - endio(pages[i]); } vout += PAGE_SIZE; outlen -= j; pageofs = 0; } + +out: preempt_enable();
if (clusterpages == 1)