diff options
Diffstat (limited to 'fs/verity')
-rw-r--r-- | fs/verity/fsverity_private.h | 1 | ||||
-rw-r--r-- | fs/verity/open.c | 1 | ||||
-rw-r--r-- | fs/verity/verify.c | 48 |
3 files changed, 24 insertions, 26 deletions
diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h index a6a6b2749241..b3506f56e180 100644 --- a/fs/verity/fsverity_private.h +++ b/fs/verity/fsverity_private.h @@ -69,7 +69,6 @@ struct fsverity_info { u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE]; const struct inode *inode; unsigned long *hash_block_verified; - spinlock_t hash_page_init_lock; }; #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ diff --git a/fs/verity/open.c b/fs/verity/open.c index 6c31a871b84b..fdeb95eca3af 100644 --- a/fs/verity/open.c +++ b/fs/verity/open.c @@ -239,7 +239,6 @@ struct fsverity_info *fsverity_create_info(const struct inode *inode, err = -ENOMEM; goto fail; } - spin_lock_init(&vi->hash_page_init_lock); } return vi; diff --git a/fs/verity/verify.c b/fs/verity/verify.c index 904ccd7e8e16..4fcad0825a12 100644 --- a/fs/verity/verify.c +++ b/fs/verity/verify.c @@ -19,7 +19,6 @@ static struct workqueue_struct *fsverity_read_workqueue; static bool is_hash_block_verified(struct fsverity_info *vi, struct page *hpage, unsigned long hblock_idx) { - bool verified; unsigned int blocks_per_page; unsigned int i; @@ -43,12 +42,20 @@ static bool is_hash_block_verified(struct fsverity_info *vi, struct page *hpage, * re-instantiated from the backing storage are re-verified. To do * this, we use PG_checked again, but now it doesn't really mean * "checked". Instead, now it just serves as an indicator for whether - * the hash page is newly instantiated or not. + * the hash page is newly instantiated or not. If the page is new, as + * indicated by PG_checked=0, we clear the bitmap bits for the page's + * blocks since they are untrustworthy, then set PG_checked=1. + * Otherwise we return the bitmap bit for the requested block. * - * The first thread that sees PG_checked=0 must clear the corresponding - * bitmap bits, then set PG_checked=1. This requires a spinlock. To - * avoid having to take this spinlock in the common case of - * PG_checked=1, we start with an opportunistic lockless read. + * Multiple threads may execute this code concurrently on the same page. + * This is safe because we use memory barriers to ensure that if a + * thread sees PG_checked=1, then it also sees the associated bitmap + * clearing to have occurred. Also, all writes and their corresponding + * reads are atomic, and all writes are safe to repeat in the event that + * multiple threads get into the PG_checked=0 section. (Clearing a + * bitmap bit again at worst causes a hash block to be verified + * redundantly. That event should be very rare, so it's not worth using + * a lock to avoid. Setting PG_checked again has no effect.) */ if (PageChecked(hpage)) { /* @@ -58,24 +65,17 @@ static bool is_hash_block_verified(struct fsverity_info *vi, struct page *hpage, smp_rmb(); return test_bit(hblock_idx, vi->hash_block_verified); } - spin_lock(&vi->hash_page_init_lock); - if (PageChecked(hpage)) { - verified = test_bit(hblock_idx, vi->hash_block_verified); - } else { - blocks_per_page = vi->tree_params.blocks_per_page; - hblock_idx = round_down(hblock_idx, blocks_per_page); - for (i = 0; i < blocks_per_page; i++) - clear_bit(hblock_idx + i, vi->hash_block_verified); - /* - * A write memory barrier is needed here to give RELEASE - * semantics to the below SetPageChecked() operation. - */ - smp_wmb(); - SetPageChecked(hpage); - verified = false; - } - spin_unlock(&vi->hash_page_init_lock); - return verified; + blocks_per_page = vi->tree_params.blocks_per_page; + hblock_idx = round_down(hblock_idx, blocks_per_page); + for (i = 0; i < blocks_per_page; i++) + clear_bit(hblock_idx + i, vi->hash_block_verified); + /* + * A write memory barrier is needed here to give RELEASE semantics to + * the below SetPageChecked() operation. + */ + smp_wmb(); + SetPageChecked(hpage); + return false; } /* |