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Subject[PATCH] zram: fix random data read
Date
fd1a30de makes a bug that it uses (struct page *) as zsmalloc's handle
although it's a uncompressed page so that it can access random page,
return random data or even crashed by get_first_page in zs_map_object.

Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
drivers/staging/zram/zram_drv.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index abd69d1..0cdc303 100644
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -280,26 +280,27 @@ static int zram_read_before_write(struct zram *zram, char *mem, u32 index)
size_t clen = PAGE_SIZE;
struct zobj_header *zheader;
unsigned char *cmem;
+ unsigned long handle = zram->table[index].handle;

- if (zram_test_flag(zram, index, ZRAM_ZERO) ||
- !zram->table[index].handle) {
+ if (zram_test_flag(zram, index, ZRAM_ZERO) || !handle) {
memset(mem, 0, PAGE_SIZE);
return 0;
}

- cmem = zs_map_object(zram->mem_pool, zram->table[index].handle);
-
/* Page is stored uncompressed since it's incompressible */
if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
- memcpy(mem, cmem, PAGE_SIZE);
- kunmap_atomic(cmem);
+ char *src = kmap_atomic((struct page *)handle);
+ memcpy(mem, src, PAGE_SIZE);
+ kunmap_atomic(src);
return 0;
}

+ cmem = zs_map_object(zram->mem_pool, handle);
+
ret = lzo1x_decompress_safe(cmem + sizeof(*zheader),
zram->table[index].size,
mem, &clen);
- zs_unmap_object(zram->mem_pool, zram->table[index].handle);
+ zs_unmap_object(zram->mem_pool, handle);

/* Should NEVER happen. Return bio error if it does. */
if (unlikely(ret != LZO_E_OK)) {
--
1.7.9.5


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