From: pengfuyuan pengfuyuan@kylinos.cn
commit 5ad9b4719fc9bc4715c7e19875a962095b0577e7 upstream.
When compiling on a MIPS 64-bit machine we get these warnings:
In file included from ./arch/mips/include/asm/cacheflush.h:13, from ./include/linux/cacheflush.h:5, from ./include/linux/highmem.h:8, from ./include/linux/bvec.h:10, from ./include/linux/blk_types.h:10, from ./include/linux/blkdev.h:9, from fs/btrfs/disk-io.c:7: fs/btrfs/disk-io.c: In function ‘csum_tree_block’: fs/btrfs/disk-io.c:100:34: error: array subscript 1 is above array bounds of ‘struct page *[1]’ [-Werror=array-bounds] 100 | kaddr = page_address(buf->pages[i]); | ~~~~~~~~~~^~~ ./include/linux/mm.h:2135:48: note: in definition of macro ‘page_address’ 2135 | #define page_address(page) lowmem_page_address(page) | ^~~~ cc1: all warnings being treated as errors
We can check if i overflows to solve the problem. However, this doesn't make much sense, since i == 1 and num_pages == 1 doesn't execute the body of the loop. In addition, i < num_pages can also ensure that buf->pages[i] will not cross the boundary. Unfortunately, this doesn't help with the problem observed here: gcc still complains.
To fix this add a compile-time condition for the extent buffer page array size limit, which would eventually lead to eliminating the whole for loop.
CC: stable@vger.kernel.org # 5.10+ Signed-off-by: pengfuyuan pengfuyuan@kylinos.cn Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/disk-io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -220,7 +220,7 @@ static void csum_tree_block(struct exten crypto_shash_update(shash, kaddr + BTRFS_CSUM_SIZE, PAGE_SIZE - BTRFS_CSUM_SIZE);
- for (i = 1; i < num_pages; i++) { + for (i = 1; i < num_pages && INLINE_EXTENT_BUFFER_PAGES > 1; i++) { kaddr = page_address(buf->pages[i]); crypto_shash_update(shash, kaddr, PAGE_SIZE); }