From 80f6e3080bfcf865062a926817b3ca6c4a137a57 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Thu, 16 Sep 2021 13:34:24 -0700 Subject: fs-verity: fix signed integer overflow with i_size near S64_MAX If the file size is almost S64_MAX, the calculated number of Merkle tree levels exceeds FS_VERITY_MAX_LEVELS, causing FS_IOC_ENABLE_VERITY to fail. This is unintentional, since as the comment above the definition of FS_VERITY_MAX_LEVELS states, it is enough for over U64_MAX bytes of data using SHA-256 and 4K blocks. (Specifically, 4096*128**8 >= 2**64.) The bug is actually that when the number of blocks in the first level is calculated from i_size, there is a signed integer overflow due to i_size being signed. Fix this by treating i_size as unsigned. This was found by the new test "generic: test fs-verity EFBIG scenarios" (https://lkml.kernel.org/r/b1d116cd4d0ea74b9cd86f349c672021e005a75c.1631558495.git.boris@bur.io). This didn't affect ext4 or f2fs since those have a smaller maximum file size, but it did affect btrfs which allows files up to S64_MAX bytes. Reported-by: Boris Burkov Fixes: 3fda4c617e84 ("fs-verity: implement FS_IOC_ENABLE_VERITY ioctl") Fixes: fd2d1acfcadf ("fs-verity: add the hook for file ->open()") Cc: # v5.4+ Reviewed-by: Boris Burkov Link: https://lore.kernel.org/r/20210916203424.113376-1-ebiggers@kernel.org Signed-off-by: Eric Biggers --- fs/verity/open.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/verity/open.c') diff --git a/fs/verity/open.c b/fs/verity/open.c index 60ff8af7219f..92df87f5fa38 100644 --- a/fs/verity/open.c +++ b/fs/verity/open.c @@ -89,7 +89,7 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, */ /* Compute number of levels and the number of blocks in each level */ - blocks = (inode->i_size + params->block_size - 1) >> log_blocksize; + blocks = ((u64)inode->i_size + params->block_size - 1) >> log_blocksize; pr_debug("Data is %lld bytes (%llu blocks)\n", inode->i_size, blocks); while (blocks > 1) { if (params->num_levels >= FS_VERITY_MAX_LEVELS) { -- cgit v1.2.3