[lxc-devel] [lxc/master] seccomp: fixes

[brauner on Github]

A non-text attachment was scrubbed...
Name: not available
Type: text/x-mailbox
Size: 406 bytes
Desc: not available
URL: <http://lists.linuxcontainers.org/pipermail/lxc-devel/attachments/20201102/ea964f80/attachment.bin>
-------------- next part --------------
From a60c98aaf637f3cb8ef6b054cceab666d2317615 Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Mon, 2 Nov 2020 16:44:05 +0100
Subject: [PATCH 1/2] seccomp: make seccomp notifier fd non-blocking

Suggested-by: Jann Horn <jann at thejh.net>
Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 src/lxc/file_utils.c | 12 ++++++++++++
 src/lxc/file_utils.h |  1 +
 src/lxc/seccomp.c    |  3 +++
 3 files changed, 16 insertions(+)

diff --git a/src/lxc/file_utils.c b/src/lxc/file_utils.c
index 4a8c7a8d99..fafaba354c 100644
--- a/src/lxc/file_utils.c
+++ b/src/lxc/file_utils.c
@@ -577,3 +577,15 @@ int open_beneath(int dir_fd, const char *path, unsigned int flags)
 
 	return openat(dir_fd, path, O_NOFOLLOW | flags);
 }
+
+int fd_make_nonblocking(int fd)
+{
+	int flags;
+
+	flags = fcntl(fd, F_GETFL);
+	if (flags < 0)
+		return -1;
+
+	flags &= ~O_NONBLOCK;
+	return fcntl(fd, F_SETFL, flags);
+}
diff --git a/src/lxc/file_utils.h b/src/lxc/file_utils.h
index df3a00d4dc..ea9570dd18 100644
--- a/src/lxc/file_utils.h
+++ b/src/lxc/file_utils.h
@@ -76,5 +76,6 @@ __hidden extern int timens_offset_write(clockid_t clk_id, int64_t s_offset, int6
 __hidden extern bool exists_dir_at(int dir_fd, const char *path);
 __hidden extern bool exists_file_at(int dir_fd, const char *path);
 __hidden extern int open_beneath(int dir_fd, const char *path, unsigned int flags);
+__hidden int fd_make_nonblocking(int fd);
 
 #endif /* __LXC_FILE_UTILS_H */
diff --git a/src/lxc/seccomp.c b/src/lxc/seccomp.c
index 4faf693f6c..e303561bf9 100644
--- a/src/lxc/seccomp.c
+++ b/src/lxc/seccomp.c
@@ -1280,6 +1280,9 @@ int lxc_seccomp_load(struct lxc_conf *conf)
 			return -1;
 		}
 
+		if (fd_make_nonblocking(ret))
+			return log_error_errno(-1, errno, "Failed to make seccomp listener fd non-blocking");;
+
 		conf->seccomp.notifier.notify_fd = ret;
 		TRACE("Retrieved new seccomp listener fd %d", ret);
 	}

From 0d724ab4f4b2611f5d93525ef8ef4f1c6d91334d Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Mon, 2 Nov 2020 16:48:02 +0100
Subject: [PATCH 2/2] seccomp: log aborted system calls

Suggested-by: Jann Horn <jann at thejh.net>
Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 src/lxc/seccomp.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/lxc/seccomp.c b/src/lxc/seccomp.c
index e303561bf9..ba6811d903 100644
--- a/src/lxc/seccomp.c
+++ b/src/lxc/seccomp.c
@@ -1390,7 +1390,10 @@ int seccomp_notify_handler(int fd, uint32_t events, void *data,
 	memset(req, 0, conf->seccomp.notifier.sizes.seccomp_notif);
 	ret = seccomp_notify_receive(fd, req);
 	if (ret) {
-		SYSERROR("Failed to read seccomp notification");
+		if (errno == ENOENT)
+			TRACE("Intercepted system call aborted");
+		else
+			SYSERROR("Failed to read seccomp notification");
 		goto out;
 	}