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authorEric Biggers <ebiggers@google.com>2021-09-16 13:34:24 -0700
committerEric Biggers <ebiggers@google.com>2021-09-22 10:56:34 -0700
commit80f6e3080bfcf865062a926817b3ca6c4a137a57 (patch)
tree0e1b571d69cfc6874266e5f513ab0d12686cb47e /fs/verity
parente4e737bb5c170df6135a127739a9e6148ee3da82 (diff)
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 <boris@bur.io> Fixes: 3fda4c617e84 ("fs-verity: implement FS_IOC_ENABLE_VERITY ioctl") Fixes: fd2d1acfcadf ("fs-verity: add the hook for file ->open()") Cc: <stable@vger.kernel.org> # v5.4+ Reviewed-by: Boris Burkov <boris@bur.io> Link: https://lore.kernel.org/r/20210916203424.113376-1-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
Diffstat (limited to 'fs/verity')
-rw-r--r--fs/verity/enable.c2
-rw-r--r--fs/verity/open.c2
2 files changed, 2 insertions, 2 deletions
diff --git a/fs/verity/enable.c b/fs/verity/enable.c
index 77e159a0346b..60a4372aa4d7 100644
--- a/fs/verity/enable.c
+++ b/fs/verity/enable.c
@@ -177,7 +177,7 @@ static int build_merkle_tree(struct file *filp,
* (level 0) and ascending to the root node (level 'num_levels - 1').
* Then at the end (level 'num_levels'), calculate the root hash.
*/
- blocks = (inode->i_size + params->block_size - 1) >>
+ blocks = ((u64)inode->i_size + params->block_size - 1) >>
params->log_blocksize;
for (level = 0; level <= params->num_levels; level++) {
err = build_merkle_tree_level(filp, level, blocks, params,
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) {