From f167d1f4e9eb24dfbda077746f25cfdf8a2b59b9 Mon Sep 17 00:00:00 2001
From: Cyrill Gorcunov <gorcunov@gmail.com>
Date: Fri, 7 Feb 2020 15:59:45 +0300
Subject: [PATCH] fown: Don't fail on dumping files opened with O_PATH

O_PATH opened files are special: they have empty
file operations in kernel space, so there not that
much we can do with them, even setting position is
not allowed. Same applies to a signal number for
owner settings.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Co-developed-by: Alexander Mikhalitsyn <alexander@mihalicyn.com>
Signed-off-by: Alexander Mikhalitsyn (Virtuozzo) <alexander@mihalicyn.com>
---
 criu/files-reg.c    | 16 +++++++---
 criu/files.c        |  5 ++-
 criu/pie/parasite.c | 75 +++++++++++++++++++++++++++++----------------
 3 files changed, 64 insertions(+), 32 deletions(-)

diff --git a/criu/files-reg.c b/criu/files-reg.c
index 0d0076666..d1d1ee5af 100644
--- a/criu/files-reg.c
+++ b/criu/files-reg.c
@@ -1776,11 +1776,17 @@ static int do_open_reg(int ns_root_fd, struct reg_file_info *rfi, void *arg)
 	if (fd < 0)
 		return fd;
 
-	if ((rfi->rfe->pos != -1ULL) &&
-			lseek(fd, rfi->rfe->pos, SEEK_SET) < 0) {
-		pr_perror("Can't restore file pos");
-		close(fd);
-		return -1;
+	/*
+	 * O_PATH opened files carry empty fops in kernel,
+	 * just ignore positioning at all.
+	 */
+	if (!(rfi->rfe->flags & O_PATH)) {
+		if (rfi->rfe->pos != -1ULL &&
+		    lseek(fd, rfi->rfe->pos, SEEK_SET) < 0) {
+			pr_perror("Can't restore file pos");
+			close(fd);
+			return -1;
+		}
 	}
 
 	return fd;
diff --git a/criu/files.c b/criu/files.c
index f7963bf54..3f1d77931 100644
--- a/criu/files.c
+++ b/criu/files.c
@@ -399,7 +399,10 @@ static int fill_fd_params(struct pid *owner_pid, int fd, int lfd,
 	pr_info("%d fdinfo %d: pos: %#16"PRIx64" flags: %16o/%#x\n",
 			owner_pid->real, fd, p->pos, p->flags, (int)p->fd_flags);
 
-	ret = fcntl(lfd, F_GETSIG, 0);
+	if (p->flags & O_PATH)
+		ret = 0;
+	else
+		ret = fcntl(lfd, F_GETSIG, 0);
 	if (ret < 0) {
 		pr_perror("Can't get owner signum on %d", lfd);
 		return -1;
diff --git a/criu/pie/parasite.c b/criu/pie/parasite.c
index 387a976da..64b5bbb3e 100644
--- a/criu/pie/parasite.c
+++ b/criu/pie/parasite.c
@@ -317,15 +317,60 @@ grps_err:
 	return -1;
 }
 
+static int fill_fds_fown(int fd, struct fd_opts *p)
+{
+	int flags, ret;
+	struct f_owner_ex owner_ex;
+	uint32_t v[2];
+
+	/*
+	 * For O_PATH opened files there is no owner at all.
+	 */
+	flags = sys_fcntl(fd, F_GETFL, 0);
+	if (flags < 0) {
+		pr_err("fcntl(%d, F_GETFL) -> %d\n", fd, flags);
+		return -1;
+	}
+	if (flags & O_PATH) {
+		p->fown.pid = 0;
+		return 0;
+	}
+
+	ret = sys_fcntl(fd, F_GETOWN_EX, (long)&owner_ex);
+	if (ret) {
+		pr_err("fcntl(%d, F_GETOWN_EX) -> %d\n", fd, ret);
+		return -1;
+	}
+
+	/*
+	 * Simple case -- nothing is changed.
+	 */
+	if (owner_ex.pid == 0) {
+		p->fown.pid = 0;
+		return 0;
+	}
+
+	ret = sys_fcntl(fd, F_GETOWNER_UIDS, (long)&v);
+	if (ret) {
+		pr_err("fcntl(%d, F_GETOWNER_UIDS) -> %d\n", fd, ret);
+		return -1;
+	}
+
+	p->fown.uid	 = v[0];
+	p->fown.euid	 = v[1];
+	p->fown.pid_type = owner_ex.type;
+	p->fown.pid	 = owner_ex.pid;
+
+	return 0;
+}
+
 static int fill_fds_opts(struct parasite_drain_fd *fds, struct fd_opts *opts)
 {
 	int i;
 
 	for (i = 0; i < fds->nr_fds; i++) {
-		int flags, fd = fds->fds[i], ret;
+		int flags, fd = fds->fds[i];
 		struct fd_opts *p = opts + i;
-		struct f_owner_ex owner_ex;
-		uint32_t v[2];
 
 		flags = sys_fcntl(fd, F_GETFD, 0);
 		if (flags < 0) {
@@ -335,30 +380,8 @@ static int fill_fds_opts(struct parasite_drain_fd *fds, struct fd_opts *opts)
 
 		p->flags = (char)flags;
 
-		ret = sys_fcntl(fd, F_GETOWN_EX, (long)&owner_ex);
-		if (ret) {
-			pr_err("fcntl(%d, F_GETOWN_EX) -> %d\n", fd, ret);
+		if (fill_fds_fown(fd, p))
 			return -1;
-		}
-
-		/*
-		 * Simple case -- nothing is changed.
-		 */
-		if (owner_ex.pid == 0) {
-			p->fown.pid = 0;
-			continue;
-		}
-
-		ret = sys_fcntl(fd, F_GETOWNER_UIDS, (long)&v);
-		if (ret) {
-			pr_err("fcntl(%d, F_GETOWNER_UIDS) -> %d\n", fd, ret);
-			return -1;
-		}
-
-		p->fown.uid	 = v[0];
-		p->fown.euid	 = v[1];
-		p->fown.pid_type = owner_ex.type;
-		p->fown.pid	 = owner_ex.pid;
 	}
 
 	return 0;