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fsverity: simplify error handling in verify_data_block()

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Clean up the error handling in verify_data_block() to (a) eliminate the
'err' variable which has caused some confusion because the function
actually returns a bool, (b) reduce the compiled code size slightly, and
(c) execute one fewer branch in the success case.

Link: https://lore.kernel.org/r/20230604022312.48532-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers
2023-06-03 19:23:12 -07:00
parent d1f0c5ea04
commit 13e2408d02
1 changed files with 21 additions and 34 deletions
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55
fs/verity/verify.c
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@@ -12,23 +12,6 @@
static struct workqueue_struct *fsverity_read_workqueue; static struct workqueue_struct *fsverity_read_workqueue;
static inline int cmp_hashes(const struct fsverity_info *vi,
const u8 *want_hash, const u8 *real_hash,
u64 data_pos, int level)
{
const unsigned int hsize = vi->tree_params.digest_size;
if (memcmp(want_hash, real_hash, hsize) == 0)
return 0;
fsverity_err(vi->inode,
"FILE CORRUPTED! pos=%llu, level=%d, want_hash=%s:%*phN, real_hash=%s:%*phN",
data_pos, level,
vi->tree_params.hash_alg->name, hsize, want_hash,
vi->tree_params.hash_alg->name, hsize, real_hash);
return -EBADMSG;
}
/* /*
* Returns true if the hash block with index @hblock_idx in the tree, located in * Returns true if the hash block with index @hblock_idx in the tree, located in
* @hpage, has already been verified. * @hpage, has already been verified.
@@ -131,7 +114,6 @@ verify_data_block(struct inode *inode, struct fsverity_info *vi,
* index of that block's hash within the current level. * index of that block's hash within the current level.
*/ */
u64 hidx = data_pos >> params->log_blocksize; u64 hidx = data_pos >> params->log_blocksize;
int err;
/* Up to 1 + FS_VERITY_MAX_LEVELS pages may be mapped at once */ /* Up to 1 + FS_VERITY_MAX_LEVELS pages may be mapped at once */
BUILD_BUG_ON(1 + FS_VERITY_MAX_LEVELS > KM_MAX_IDX); BUILD_BUG_ON(1 + FS_VERITY_MAX_LEVELS > KM_MAX_IDX);
@@ -191,11 +173,10 @@ verify_data_block(struct inode *inode, struct fsverity_info *vi,
hpage_idx, level == 0 ? min(max_ra_pages, hpage_idx, level == 0 ? min(max_ra_pages,
params->tree_pages - hpage_idx) : 0); params->tree_pages - hpage_idx) : 0);
if (IS_ERR(hpage)) { if (IS_ERR(hpage)) {
err = PTR_ERR(hpage);
fsverity_err(inode, fsverity_err(inode,
"Error %d reading Merkle tree page %lu", "Error %ld reading Merkle tree page %lu",
err, hpage_idx); PTR_ERR(hpage), hpage_idx);
goto out; goto error;
} }
haddr = kmap_local_page(hpage) + hblock_offset_in_page; haddr = kmap_local_page(hpage) + hblock_offset_in_page;
if (is_hash_block_verified(vi, hpage, hblock_idx)) { if (is_hash_block_verified(vi, hpage, hblock_idx)) {
@@ -221,12 +202,10 @@ descend:
unsigned long hblock_idx = hblocks[level - 1].index; unsigned long hblock_idx = hblocks[level - 1].index;
unsigned int hoffset = hblocks[level - 1].hoffset; unsigned int hoffset = hblocks[level - 1].hoffset;
err = fsverity_hash_block(params, inode, haddr, real_hash); if (fsverity_hash_block(params, inode, haddr, real_hash) != 0)
if (err) goto error;
goto out; if (memcmp(want_hash, real_hash, hsize) != 0)
err = cmp_hashes(vi, want_hash, real_hash, data_pos, level - 1); goto corrupted;
if (err)
goto out;
/* /*
* Mark the hash block as verified. This must be atomic and * Mark the hash block as verified. This must be atomic and
* idempotent, as the same hash block might be verified by * idempotent, as the same hash block might be verified by
@@ -243,16 +222,24 @@ descend:
} }
/* Finally, verify the data block. */ /* Finally, verify the data block. */
err = fsverity_hash_block(params, inode, data, real_hash); if (fsverity_hash_block(params, inode, data, real_hash) != 0)
if (err) goto error;
goto out; if (memcmp(want_hash, real_hash, hsize) != 0)
err = cmp_hashes(vi, want_hash, real_hash, data_pos, -1); goto corrupted;
out: return true;
corrupted:
fsverity_err(inode,
"FILE CORRUPTED! pos=%llu, level=%d, want_hash=%s:%*phN, real_hash=%s:%*phN",
data_pos, level - 1,
params->hash_alg->name, hsize, want_hash,
params->hash_alg->name, hsize, real_hash);
error:
for (; level > 0; level--) { for (; level > 0; level--) {
kunmap_local(hblocks[level - 1].addr); kunmap_local(hblocks[level - 1].addr);
put_page(hblocks[level - 1].page); put_page(hblocks[level - 1].page);
} }
return err == 0; return false;
} }
static bool static bool