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VerityUtils: handle ENOTTY from FS_IOC_GETFLAGS

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In some cases, such as EROFS filesystems, it's expected for
statxForFsverity() to get ENOTTY from FS_IOC_GETFLAGS.  In this case, we
should just return 0 to indicate that fs-verity is not enabled.  This
avoids logging an ERROR message to the log unnecessarily.

Bug: 279597861
Change-Id: I58149f7611c223789210594f28a98420dfddd8ec
This commit is contained in:
Eric Biggers
2023-05-18 18:06:26 +00:00
parent 8c7dbeba13
commit 2884c77232
1 changed files with 16 additions and 3 deletions
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19
core/jni/com_android_internal_security_VerityUtils.cpp
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@@ -79,7 +79,11 @@ int enableFsverity(JNIEnv *env, jobject /* clazz */, jstring filePath, jbyteArra
int statxForFsverity(JNIEnv *env, jobject /* clazz */, jstring filePath) {
ScopedUtfChars path(env, filePath);
// Call statx and check STATX_ATTR_VERITY.
// There are two ways to check whether a file has fs-verity enabled: statx() and FS_IOC_GETFLAGS
// (See https://www.kernel.org/doc/html/latest/filesystems/fsverity.html#statx and
// https://www.kernel.org/doc/html/latest/filesystems/fsverity.html#fs-ioc-getflags.)
// We try statx() first, since it doesn't require opening the file.
struct statx out = {};
if (statx(AT_FDCWD, path.c_str(), 0 /* flags */, STATX_ALL, &out) != 0) {
return -errno;
@@ -89,8 +93,12 @@ int statxForFsverity(JNIEnv *env, jobject /* clazz */, jstring filePath) {
return (out.stx_attributes & STATX_ATTR_VERITY) != 0;
}
// STATX_ATTR_VERITY is not supported for the file path.
// In this case, call ioctl(FS_IOC_GETFLAGS) and check FS_VERITY_FL.
// The filesystem doesn't support STATX_ATTR_VERITY. This normally means that it doesn't
// support fs-verity, in which case we should simply return 0. Unfortunately, virtio-fs is an
// exception, since it doesn't support STATX_ATTR_VERITY but does support querying FS_VERITY_FL
// via FS_IOC_GETFLAGS. So we have to fall back to FS_IOC_GETFLAGS. Note: despite being an
// ioctl, FS_IOC_GETFLAGS doesn't require the "ioctl" SELinux permission but rather "getattr".
::android::base::unique_fd rfd(open(path.c_str(), O_RDONLY | O_CLOEXEC));
if (rfd.get() < 0) {
ALOGE("open failed at %s", path.c_str());
@@ -99,6 +107,11 @@ int statxForFsverity(JNIEnv *env, jobject /* clazz */, jstring filePath) {
unsigned int flags;
if (ioctl(rfd.get(), FS_IOC_GETFLAGS, &flags) < 0) {
if (errno == ENOTTY) {
// If the filesystem supports neither STATX_ATTR_VERITY nor FS_IOC_GETFLAGS, then assume
// that it doesn't support fs-verity.
return 0;
}
ALOGE("ioctl(FS_IOC_GETFLAGS) failed at %s", path.c_str());
return -errno;
}