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-rw-r--r--fs/verity/enable.c25
-rw-r--r--fs/verity/verify.c12
2 files changed, 19 insertions, 18 deletions
diff --git a/fs/verity/enable.c b/fs/verity/enable.c
index e13db6507b38..7a0e3a84d370 100644
--- a/fs/verity/enable.c
+++ b/fs/verity/enable.c
@@ -8,7 +8,6 @@
#include "fsverity_private.h"
#include <linux/mount.h>
-#include <linux/pagemap.h>
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
@@ -367,25 +366,27 @@ int fsverity_ioctl_enable(struct file *filp, const void __user *uarg)
goto out_drop_write;
err = enable_verity(filp, &arg);
- if (err)
- goto out_allow_write_access;
/*
- * Some pages of the file may have been evicted from pagecache after
- * being used in the Merkle tree construction, then read into pagecache
- * again by another process reading from the file concurrently. Since
- * these pages didn't undergo verification against the file digest which
- * fs-verity now claims to be enforcing, we have to wipe the pagecache
- * to ensure that all future reads are verified.
+ * We no longer drop the inode's pagecache after enabling verity. This
+ * used to be done to try to avoid a race condition where pages could be
+ * evicted after being used in the Merkle tree construction, then
+ * re-instantiated by a concurrent read. Such pages are unverified, and
+ * the backing storage could have filled them with different content, so
+ * they shouldn't be used to fulfill reads once verity is enabled.
+ *
+ * But, dropping the pagecache has a big performance impact, and it
+ * doesn't fully solve the race condition anyway. So for those reasons,
+ * and also because this race condition isn't very important relatively
+ * speaking (especially for small-ish files, where the chance of a page
+ * being used, evicted, *and* re-instantiated all while enabling verity
+ * is quite small), we no longer drop the inode's pagecache.
*/
- filemap_write_and_wait(inode->i_mapping);
- invalidate_inode_pages2(inode->i_mapping);
/*
* allow_write_access() is needed to pair with deny_write_access().
* Regardless, the filesystem won't allow writing to verity files.
*/
-out_allow_write_access:
allow_write_access(filp);
out_drop_write:
mnt_drop_write_file(filp);
diff --git a/fs/verity/verify.c b/fs/verity/verify.c
index f50e3b5b52c9..e2508222750b 100644
--- a/fs/verity/verify.c
+++ b/fs/verity/verify.c
@@ -387,15 +387,15 @@ EXPORT_SYMBOL_GPL(fsverity_enqueue_verify_work);
int __init fsverity_init_workqueue(void)
{
/*
- * Use an unbound workqueue to allow bios to be verified in parallel
- * even when they happen to complete on the same CPU. This sacrifices
- * locality, but it's worthwhile since hashing is CPU-intensive.
+ * Use a high-priority workqueue to prioritize verification work, which
+ * blocks reads from completing, over regular application tasks.
*
- * Also use a high-priority workqueue to prioritize verification work,
- * which blocks reads from completing, over regular application tasks.
+ * For performance reasons, don't use an unbound workqueue. Using an
+ * unbound workqueue for crypto operations causes excessive scheduler
+ * latency on ARM64.
*/
fsverity_read_workqueue = alloc_workqueue("fsverity_read_queue",
- WQ_UNBOUND | WQ_HIGHPRI,
+ WQ_HIGHPRI,
num_online_cpus());
if (!fsverity_read_workqueue)
return -ENOMEM;