lkml.org 
[lkml]   [2023]   [Mar]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
Subject[PATCH 3/3] fanotify: use pidfd_prepare()
We generally try to avoid installing a file descriptor into the caller's
file descriptor table just to close it again via close_fd() in case an
error occurs. Instead we reserve a file descriptor but don't install it
into the caller's file descriptor table yet. If we fail for other,
unrelated reasons we can just close the reserved file descriptor and if
we make it past all meaningful error paths we just install it. Fanotify
gets this right already for one fd type but not for pidfds.

Use the new pidfd_prepare() helper to reserve a pidfd and a pidfd file
and switch to the more common fd allocation and installation pattern.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
fs/notify/fanotify/fanotify_user.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 8f430bfad487..22fb1cf7e1fc 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -663,7 +663,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
struct fanotify_info *info = fanotify_event_info(event);
unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES);
unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD;
- struct file *f = NULL;
+ struct file *f = NULL, *pidfd_file = NULL;
int ret, pidfd = FAN_NOPIDFD, fd = FAN_NOFD;

pr_debug("%s: group=%p event=%p\n", __func__, group, event);
@@ -718,7 +718,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
!pid_has_task(event->pid, PIDTYPE_TGID)) {
pidfd = FAN_NOPIDFD;
} else {
- pidfd = pidfd_create(event->pid, 0);
+ pidfd = pidfd_prepare(event->pid, 0, &pidfd_file);
if (pidfd < 0)
pidfd = FAN_EPIDFD;
}
@@ -751,6 +751,9 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
if (f)
fd_install(fd, f);

+ if (pidfd_file)
+ fd_install(pidfd, pidfd_file);
+
return metadata.event_len;

out_close_fd:
@@ -759,8 +762,10 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
fput(f);
}

- if (pidfd >= 0)
- close_fd(pidfd);
+ if (pidfd >= 0) {
+ put_unused_fd(pidfd);
+ fput(pidfd_file);
+ }

return ret;
}
--
2.34.1

\
 
 \ /
  Last update: 2023-03-27 20:24    [W:0.040 / U:1.112 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site