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authorMike Christie <michael.christie@oracle.com>2023-03-10 16:03:27 -0600
committerChristian Brauner (Microsoft) <brauner@kernel.org>2023-03-12 10:54:43 +0100
commit11f3f500ec8a75c96087f3bed87aa2b1c5de7498 (patch)
tree08d3834456a1139b1a6a3f059d13713bc8c268e2 /kernel/fork.c
parent54e6842d0775ba76db65cbe21311c3ca466e663d (diff)
fork: add kernel_clone_args flag to not dup/clone files
Each vhost device gets a thread that is used to perform IO and management operations. Instead of a thread that is accessing a device, the thread is part of the device, so when it creates a thread using a helper based on copy_process we can't dup or clone the parent's files/FDS because it would do an extra increment on ourself. Later, when we do: Qemu process exits: do_exit -> exit_files -> put_files_struct -> close_files we would leak the device's resources because of that extra refcount on the fd or file_struct. This patch adds a no_files option so these worker threads can prevent taking an extra refcount on themselves. Signed-off-by: Mike Christie <michael.christie@oracle.com> Acked-by: Christian Brauner <brauner@kernel.org> Acked-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index fb8ec192c199..f8d530f4406e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1627,7 +1627,8 @@ static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
return 0;
}
-static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
+static int copy_files(unsigned long clone_flags, struct task_struct *tsk,
+ int no_files)
{
struct files_struct *oldf, *newf;
int error = 0;
@@ -1639,6 +1640,11 @@ static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
if (!oldf)
goto out;
+ if (no_files) {
+ tsk->files = NULL;
+ goto out;
+ }
+
if (clone_flags & CLONE_FILES) {
atomic_inc(&oldf->count);
goto out;
@@ -2259,7 +2265,7 @@ static __latent_entropy struct task_struct *copy_process(
retval = copy_semundo(clone_flags, p);
if (retval)
goto bad_fork_cleanup_security;
- retval = copy_files(clone_flags, p);
+ retval = copy_files(clone_flags, p, args->no_files);
if (retval)
goto bad_fork_cleanup_semundo;
retval = copy_fs(clone_flags, p);