diff mbox series

[v2,2/5] kernel/pid.c: implement additional checks upon pidfd_create() parameters

Message ID 3020418a466bc3f4e90413c3c98c29a1a93fd59f.1623282854.git.repnop@google.com (mailing list archive)
State New
Headers show
Series Add pidfd support to the fanotify API | expand

Commit Message

Matthew Bobrowski June 10, 2021, 12:20 a.m. UTC
By adding the pidfd_create() declaration to linux/pid.h, we
effectively expose this function to the rest of the kernel. In order
to avoid any unintended behaviour, or set false expectations upon this
function, ensure that constraints are forced upon each of the passed
parameters. This includes the checking of whether the passed struct
pid is a thread-group leader as pidfd creation is currently limited to
such pid types.

Signed-off-by: Matthew Bobrowski <repnop@google.com>
---
 kernel/pid.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

Comments

Christian Brauner June 15, 2021, 11:35 a.m. UTC | #1
On Thu, Jun 10, 2021 at 10:20:43AM +1000, Matthew Bobrowski wrote:
> By adding the pidfd_create() declaration to linux/pid.h, we
> effectively expose this function to the rest of the kernel. In order
> to avoid any unintended behaviour, or set false expectations upon this
> function, ensure that constraints are forced upon each of the passed
> parameters. This includes the checking of whether the passed struct
> pid is a thread-group leader as pidfd creation is currently limited to
> such pid types.
> 
> Signed-off-by: Matthew Bobrowski <repnop@google.com>
> ---

Looks good,
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
diff mbox series

Patch

diff --git a/kernel/pid.c b/kernel/pid.c
index d3cd95b8b080..efe87db44683 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -559,6 +559,12 @@  int pidfd_create(struct pid *pid, unsigned int flags)
 {
 	int fd;
 
+	if (!pid || !pid_has_task(pid, PIDTYPE_TGID))
+		return -EINVAL;
+
+	if (flags & ~(O_NONBLOCK | O_RDWR | O_CLOEXEC))
+		return -EINVAL;
+
 	fd = anon_inode_getfd("[pidfd]", &pidfd_fops, get_pid(pid),
 			      flags | O_RDWR | O_CLOEXEC);
 	if (fd < 0)
@@ -598,10 +604,7 @@  SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags)
 	if (!p)
 		return -ESRCH;
 
-	if (pid_has_task(p, PIDTYPE_TGID))
-		fd = pidfd_create(p, flags);
-	else
-		fd = -EINVAL;
+	fd = pidfd_create(p, flags);
 
 	put_pid(p);
 	return fd;