libfs: Fix shift bug in generic_check_addressable()
generic_check_addressable() erroneously shifts pages down by a block
factor when it should be shifting up. To prevent overflow, we shift
blocks down to pages.
Signed-off-by: Joel Becker <joel.becker@oracle.com>
diff --git a/fs/libfs.c b/fs/libfs.c
index 8debe7b..62baa03 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -925,6 +925,8 @@
int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
{
u64 last_fs_block = num_blocks - 1;
+ u64 last_fs_page =
+ last_fs_block >> (PAGE_CACHE_SHIFT - blocksize_bits);
if (unlikely(num_blocks == 0))
return 0;
@@ -932,10 +934,8 @@
if ((blocksize_bits < 9) || (blocksize_bits > PAGE_CACHE_SHIFT))
return -EINVAL;
- if ((last_fs_block >
- (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
- (last_fs_block >
- (pgoff_t)(~0ULL) >> (PAGE_CACHE_SHIFT - blocksize_bits))) {
+ if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
+ (last_fs_page > (pgoff_t)(~0ULL))) {
return -EFBIG;
}
return 0;
