lkml.org 
[lkml]   [2019]   [Feb]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 1/3] staging: erofs: compressed_pages should not be accessed again after freed
Date
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>
---
drivers/staging/erofs/unzip_vle.c | 38 ++++++++++++++++++-----------------
drivers/staging/erofs/unzip_vle.h | 3 +--
drivers/staging/erofs/unzip_vle_lz4.c | 19 ++++++++----------
3 files changed, 29 insertions(+), 31 deletions(-)

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)
--
2.14.5
\
 
 \ /
  Last update: 2019-02-27 06:36    [W:0.045 / U:27.544 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site