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| author | Eric Biggers <ebiggers@google.com> | 2021-09-16 22:34:24 +0200 |
|---|---|---|
| committer | Eric Biggers <ebiggers@google.com> | 2021-09-22 19:56:34 +0200 |
| commit | 80f6e3080bfcf865062a926817b3ca6c4a137a57 (patch) | |
| tree | 0e1b571d69cfc6874266e5f513ab0d12686cb47e | |
| parent | Linux 5.15-rc2 (diff) | |
| download | linux-80f6e3080bfcf865062a926817b3ca6c4a137a57.tar.xz linux-80f6e3080bfcf865062a926817b3ca6c4a137a57.zip | |
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>
| -rw-r--r-- | fs/verity/enable.c | 2 | ||||
| -rw-r--r-- | fs/verity/open.c | 2 |
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) { |