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zram: fix null dereference of handle 

In testing I found handle passed to zs_map_object in __zram_bvec_read is
NULL so eh kernel goes oops in pin_object().

The reason is there is no routine to check the slot's freeing after
getting the slot's lock.  This patch fixes it.

[minchan@kernel.org: v2]
  Link: http://lkml.kernel.org/r/1505887347-10881-1-git-send-email-minchan@kernel.org
Link: http://lkml.kernel.org/r/1505788488-26723-1-git-send-email-minchan@kernel.org
Fixes: 1f7319c742 ("zram: partial IO refactoring")
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Minchan Kim 2017-10-03 16:15:19 -07:00 committed by Linus Torvalds
parent a872eb2131
commit ae94264ed4
1 changed files with 12 additions and 24 deletions
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36
drivers/block/zram/zram_drv.c
View File

@ -766,27 +766,6 @@ static void zram_slot_unlock(struct zram *zram, u32 index)
bit_spin_unlock(ZRAM_ACCESS, &zram->table[index].value);
}
static bool zram_same_page_read(struct zram *zram, u32 index,
struct page *page,
unsigned int offset, unsigned int len)
{
zram_slot_lock(zram, index);
if (unlikely(!zram_get_handle(zram, index) ||
zram_test_flag(zram, index, ZRAM_SAME))) {
void *mem;
zram_slot_unlock(zram, index);
mem = kmap_atomic(page);
zram_fill_page(mem + offset, len,
zram_get_element(zram, index));
kunmap_atomic(mem);
return true;
}
zram_slot_unlock(zram, index);
return false;
}
static void zram_meta_free(struct zram *zram, u64 disksize)
{
size_t num_pages = disksize >> PAGE_SHIFT;
@ -884,11 +863,20 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
zram_slot_unlock(zram, index);
}
if (zram_same_page_read(zram, index, page, 0, PAGE_SIZE))
return 0;
zram_slot_lock(zram, index);
handle = zram_get_handle(zram, index);
if (!handle || zram_test_flag(zram, index, ZRAM_SAME)) {
unsigned long value;
void *mem;
value = handle ? zram_get_element(zram, index) : 0;
mem = kmap_atomic(page);
zram_fill_page(mem, PAGE_SIZE, value);
kunmap_atomic(mem);
zram_slot_unlock(zram, index);
return 0;
}
size = zram_get_obj_size(zram, index);
src = zs_map_object(zram->mem_pool, handle, ZS_MM_RO);