linux-kernel - [PATCH v2] fsverity: use WARN_ON_ONCE instead of WARN

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Date:   Thu,  6 Apr 2023 11:15:42 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     fsverity@...ts.linux.dev
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chaitanya Kulkarni <kch@...dia.com>
Subject: [PATCH v2] fsverity: use WARN_ON_ONCE instead of WARN_ON

From: Eric Biggers <ebiggers@...gle.com>

As per Linus's suggestion
(https://lore.kernel.org/r/CAHk-=whefxRGyNGzCzG6BVeM=5vnvgb-XhSeFJVxJyAxAF8XRA@mail.gmail.com),
use WARN_ON_ONCE instead of WARN_ON.  This barely adds any extra
overhead, and it makes it so that if any of these ever becomes reachable
(they shouldn't, but that's the point), the logs can't be flooded.

Reviewed-by: Chaitanya Kulkarni <kch@...dia.com>
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 fs/verity/enable.c       | 4 ++--
 fs/verity/hash_algs.c    | 4 ++--
 fs/verity/open.c         | 2 +-
 include/linux/fsverity.h | 6 +++---
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/verity/enable.c b/fs/verity/enable.c
index 7a0e3a84d370b..541c2a277c5c6 100644
--- a/fs/verity/enable.c
+++ b/fs/verity/enable.c
@@ -165,7 +165,7 @@ static int build_merkle_tree(struct file *filp,
 		}
 	}
 	/* The root hash was filled by the last call to hash_one_block(). */
-	if (WARN_ON(buffers[num_levels].filled != params->digest_size)) {
+	if (WARN_ON_ONCE(buffers[num_levels].filled != params->digest_size)) {
 		err = -EINVAL;
 		goto out;
 	}
@@ -277,7 +277,7 @@ static int enable_verity(struct file *filp,
 		fsverity_err(inode, "%ps() failed with err %d",
 			     vops->end_enable_verity, err);
 		fsverity_free_info(vi);
-	} else if (WARN_ON(!IS_VERITY(inode))) {
+	} else if (WARN_ON_ONCE(!IS_VERITY(inode))) {
 		err = -EINVAL;
 		fsverity_free_info(vi);
 	} else {
diff --git a/fs/verity/hash_algs.c b/fs/verity/hash_algs.c
index 13fcf31be8441..ea00dbedf756b 100644
--- a/fs/verity/hash_algs.c
+++ b/fs/verity/hash_algs.c
@@ -84,9 +84,9 @@ struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
 	}
 
 	err = -EINVAL;
-	if (WARN_ON(alg->digest_size != crypto_ahash_digestsize(tfm)))
+	if (WARN_ON_ONCE(alg->digest_size != crypto_ahash_digestsize(tfm)))
 		goto err_free_tfm;
-	if (WARN_ON(alg->block_size != crypto_ahash_blocksize(tfm)))
+	if (WARN_ON_ONCE(alg->block_size != crypto_ahash_blocksize(tfm)))
 		goto err_free_tfm;
 
 	err = mempool_init_kmalloc_pool(&alg->req_pool, 1,
diff --git a/fs/verity/open.c b/fs/verity/open.c
index 9366b441d01ca..52048b7630dcc 100644
--- a/fs/verity/open.c
+++ b/fs/verity/open.c
@@ -83,7 +83,7 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
 	params->log_blocks_per_page = PAGE_SHIFT - log_blocksize;
 	params->blocks_per_page = 1 << params->log_blocks_per_page;
 
-	if (WARN_ON(!is_power_of_2(params->digest_size))) {
+	if (WARN_ON_ONCE(!is_power_of_2(params->digest_size))) {
 		err = -EINVAL;
 		goto out_err;
 	}
diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h
index 119a3266791fd..e76605d5b36ee 100644
--- a/include/linux/fsverity.h
+++ b/include/linux/fsverity.h
@@ -233,18 +233,18 @@ static inline int fsverity_ioctl_read_metadata(struct file *filp,
 static inline bool fsverity_verify_blocks(struct folio *folio, size_t len,
 					  size_t offset)
 {
-	WARN_ON(1);
+	WARN_ON_ONCE(1);
 	return false;
 }
 
 static inline void fsverity_verify_bio(struct bio *bio)
 {
-	WARN_ON(1);
+	WARN_ON_ONCE(1);
 }
 
 static inline void fsverity_enqueue_verify_work(struct work_struct *work)
 {
-	WARN_ON(1);
+	WARN_ON_ONCE(1);
 }
 
 #endif	/* !CONFIG_FS_VERITY */

base-commit: 1238c8b91c5aca6dd13bccb1b4dc716718e7bfac
-- 
2.40.0