On Thu 16-07-26 13:27:22, Li Chen wrote: > PIDFD_THREAD shares O_EXCL. do_dentry_open() clears O_EXCL after > pidfs_export_open() validates the flags, so open_by_handle_at() > silently turns a thread pidfd into a process pidfd. > > Restore PIDFD_THREAD on the opened file, matching pidfs_alloc_file(), > and cover the restored flag with F_GETFL. > > Signed-off-by: Li Chen <[email protected]>
Makes sense. Just looking at this code, what about PIDFD_AUTOKILL (aka O_TRUNC?)? Reading the commit introducing it 07c3ef58223e it appears it was never meant to be directly requested by userspace so probably pidfs_export_open() needs to reject it. But that's unrelated issue to your patch so feel free to add: Reviewed-by: Jan Kara <[email protected]> Honza > --- > fs/pidfs.c | 8 +++++++- > tools/testing/selftests/pidfd/pidfd_file_handle_test.c | 1 + > 2 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/fs/pidfs.c b/fs/pidfs.c > index aaa609ddab044..c20ffd747ff51 100644 > --- a/fs/pidfs.c > +++ b/fs/pidfs.c > @@ -939,12 +939,18 @@ static int pidfs_export_permission(struct > handle_to_path_ctx *ctx, > > static struct file *pidfs_export_open(const struct path *path, unsigned int > oflags) > { > + struct file *file; > + > /* > * Clear O_LARGEFILE as open_by_handle_at() forces it and raise > * O_RDWR as pidfds always are. > */ > oflags &= ~O_LARGEFILE; > - return dentry_open(path, oflags | O_RDWR, current_cred()); > + file = dentry_open(path, oflags | O_RDWR, current_cred()); > + /* do_dentry_open() strips O_EXCL, which encodes PIDFD_THREAD. */ > + if (!IS_ERR(file)) > + file->f_flags |= oflags & PIDFD_THREAD; > + return file; > } > > static const struct export_operations pidfs_export_operations = { > diff --git a/tools/testing/selftests/pidfd/pidfd_file_handle_test.c > b/tools/testing/selftests/pidfd/pidfd_file_handle_test.c > index 68918734dcf32..1e03ae9575fe6 100644 > --- a/tools/testing/selftests/pidfd/pidfd_file_handle_test.c > +++ b/tools/testing/selftests/pidfd/pidfd_file_handle_test.c > @@ -373,6 +373,7 @@ TEST_F(file_handle, open_by_handle_at_valid_flags) > O_CLOEXEC | > O_EXCL); > ASSERT_GE(pidfd, 0); > + ASSERT_NE(fcntl(pidfd, F_GETFL) & PIDFD_THREAD, 0); > > ASSERT_EQ(fstat(pidfd, &st2), 0); > ASSERT_TRUE(st1.st_dev == st2.st_dev && st1.st_ino == st2.st_ino); > -- > 2.52.0 > -- Jan Kara <[email protected]> SUSE Labs, CR
