path: root/fs/fcntl.c
diff options
authorPavel Tikhomirov <ptikhomirov@virtuozzo.com>2021-02-03 15:41:56 +0300
committerJeff Layton <jlayton@kernel.org>2021-02-08 07:36:13 -0500
commitcc4a3f885e8f2bc3c86a265972e94fef32d68f67 (patch)
treecb08cd7f4c9304655bf1385dd150c6a45f9e1384 /fs/fcntl.c
parentLinux 5.11-rc7 (diff)
fcntl: make F_GETOWN(EX) return 0 on dead owner task
Currently there is no way to differentiate the file with alive owner from the file with dead owner but pid of the owner reused. That's why CRIU can't actually know if it needs to restore file owner or not, because if it restores owner but actual owner was dead, this can introduce unexpected signals to the "false"-owner (which reused the pid). Let's change the api, so that F_GETOWN(EX) returns 0 in case actual owner is dead already. This comports with the POSIX spec, which states that a PID of 0 indicates that no signal will be sent. Cc: Jeff Layton <jlayton@kernel.org> Cc: "J. Bruce Fields" <bfields@fieldses.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: Cyrill Gorcunov <gorcunov@gmail.com> Cc: Andrei Vagin <avagin@gmail.com> Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com> Signed-off-by: Jeff Layton <jlayton@kernel.org>
Diffstat (limited to 'fs/fcntl.c')
1 files changed, 13 insertions, 6 deletions
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 05b36b28f2e8..483ef8861376 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -148,11 +148,15 @@ void f_delown(struct file *filp)
pid_t f_getown(struct file *filp)
- pid_t pid;
+ pid_t pid = 0;
- pid = pid_vnr(filp->f_owner.pid);
- if (filp->f_owner.pid_type == PIDTYPE_PGID)
- pid = -pid;
+ rcu_read_lock();
+ if (pid_task(filp->f_owner.pid, filp->f_owner.pid_type)) {
+ pid = pid_vnr(filp->f_owner.pid);
+ if (filp->f_owner.pid_type == PIDTYPE_PGID)
+ pid = -pid;
+ }
+ rcu_read_unlock();
return pid;
@@ -200,11 +204,14 @@ static int f_setown_ex(struct file *filp, unsigned long arg)
static int f_getown_ex(struct file *filp, unsigned long arg)
struct f_owner_ex __user *owner_p = (void __user *)arg;
- struct f_owner_ex owner;
+ struct f_owner_ex owner = {};
int ret = 0;
- owner.pid = pid_vnr(filp->f_owner.pid);
+ rcu_read_lock();
+ if (pid_task(filp->f_owner.pid, filp->f_owner.pid_type))
+ owner.pid = pid_vnr(filp->f_owner.pid);
+ rcu_read_unlock();
switch (filp->f_owner.pid_type) {
owner.type = F_OWNER_TID;