6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ard Biesheuvel <ardb@kernel.org>
commit b2326338dc683e8c1067c0cbf7a47986c4190902 upstream.
Ravi reports that statfs() may be called by unprivileged users on the
efivarfs mount point, which may result in a flood of calls to the
QueryVariableInfo() runtime service. These calls are disproportionately
costly on x86 systems where the variable store is backed by SMM, as each
SMM entry requires a rendez-vous of all the CPUs.
So rate limit the calls to QueryVariableInfo() at twice per second, and
return the most recently obtained value for calls that are elided.
Cc: <redacted>
Reported-by: Ravi Bangoria <redacted>
Fixes: d86ff3333cb1 ("efivarfs: expose used and total size")
Reviewed-by: Anisse Astier <redacted>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/efivarfs/super.c | 30 ++++++++++++++++++++++++------
1 file changed, 24 insertions(+), 6 deletions(-)
--- a/fs/efivarfs/super.c
+++ b/fs/efivarfs/super.c
@@ -36,12 +36,30 @@ static int efivarfs_statfs(struct dentry
/* Some UEFI firmware does not implement QueryVariableInfo() */
storage_space = remaining_space = 0;
if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) {
- status = efivar_query_variable_info(attr, &storage_space,
- &remaining_space,
- &max_variable_size);
- if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED)
- pr_warn_ratelimited("query_variable_info() failed: 0x%lx\n",
- status);
+ static DEFINE_RATELIMIT_STATE(_rs, 2 * HZ, 5);
+ static u64 storage, remaining;
+ static DEFINE_SPINLOCK(lock);
+
+ if (!__ratelimit(&_rs)) {
+ ratelimit_set_flags(&_rs, RATELIMIT_MSG_ON_RELEASE);
+
+ spin_lock(&lock);
+ storage_space = storage;
+ remaining_space = remaining;
+ spin_unlock(&lock);
+ } else {
+ status = efivar_query_variable_info(attr, &storage_space,
+ &remaining_space,
+ &max_variable_size);
+ if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED)
+ pr_warn("query_variable_info() failed: 0x%lx\n",
+ status);
+
+ spin_lock(&lock);
+ storage = storage_space;
+ remaining = remaining_space;
+ spin_unlock(&lock);
+ }
}
/*