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Handle UMOUNT_NOFOLLOW in VFS2 umount(2).

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Reported-by: syzbot+f9ecb181a4b3abdde9b9@syzkaller.appspotmail.com
Reported-by: syzbot+8c5cb9d7a044a91a513b@syzkaller.appspotmail.com
PiperOrigin-RevId: 406951359
This commit is contained in:
Ayush Ranjan
2021-11-01 16:51:12 -07:00
committed by gVisor bot
parent 9776edb3fa
commit 58017e6553
2 changed files with 36 additions and 2 deletions
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pkg/sentry/syscalls/linux/vfs2/mount.go
+2 -2
View File
@@ -136,14 +136,14 @@ func Umount2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
if err != nil {
return 0, nil, err
}
tpop, err := getTaskPathOperation(t, linux.AT_FDCWD, path, disallowEmptyPath, nofollowFinalSymlink)
tpop, err := getTaskPathOperation(t, linux.AT_FDCWD, path, disallowEmptyPath, shouldFollowFinalSymlink(flags&linux.UMOUNT_NOFOLLOW == 0))
if err != nil {
return 0, nil, err
}
defer tpop.Release(t)
opts := vfs.UmountOptions{
Flags: uint32(flags),
Flags: uint32(flags &^ linux.UMOUNT_NOFOLLOW),
}
return 0, nil, t.Kernel().VFS().UmountAt(t, creds, &tpop.pop, &opts)
test/syscalls/linux/mount.cc
+34
View File
@@ -115,6 +115,40 @@ TEST(MountTest, OpenFileBusy) {
EXPECT_THAT(umount(dir.path().c_str()), SyscallFailsWithErrno(EBUSY));
}
TEST(MountTest, UmountNoFollow) {
SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SYS_ADMIN)));
auto const dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
auto const mountPoint = NewTempAbsPathInDir(dir.path());
ASSERT_THAT(mkdir(mountPoint.c_str(), 0777), SyscallSucceeds());
// Create a symlink in dir which will point to the actual mountpoint.
const std::string symlinkInDir = NewTempAbsPathInDir(dir.path());
EXPECT_THAT(symlink(mountPoint.c_str(), symlinkInDir.c_str()),
SyscallSucceeds());
// Create a symlink to the dir.
const std::string symlinkToDir = NewTempAbsPath();
EXPECT_THAT(symlink(dir.path().c_str(), symlinkToDir.c_str()),
SyscallSucceeds());
// Should fail with ELOOP when UMOUNT_NOFOLLOW is specified and the last
// component is a symlink.
auto mount = ASSERT_NO_ERRNO_AND_VALUE(
Mount("", mountPoint, "tmpfs", 0, "mode=0700", 0));
EXPECT_THAT(umount2(symlinkInDir.c_str(), UMOUNT_NOFOLLOW),
SyscallFailsWithErrno(EINVAL));
EXPECT_THAT(unlink(symlinkInDir.c_str()), SyscallSucceeds());
// UMOUNT_NOFOLLOW should only apply to the last path component. A symlink in
// non-last path component should be just fine.
EXPECT_THAT(umount2(JoinPath(symlinkToDir, Basename(mountPoint)).c_str(),
UMOUNT_NOFOLLOW),
SyscallSucceeds());
mount.Release();
}
TEST(MountTest, UmountDetach) {
SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SYS_ADMIN)));