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authorEric W. Biederman <ebiederm@xmission.com>2020-11-20 17:14:21 -0600
committerEric W. Biederman <ebiederm@xmission.com>2020-12-10 12:39:40 -0600
commitf43c283a89a7dc531a47d4b1e001503cf3dc3234 (patch)
tree4cd07b236726827c958bfe2e67bf9f2dd2194fd3 /kernel/kcmp.c
parent950db38ff2c01b7aabbd7ab4a50b7992750fa63d (diff)
kcmp: In kcmp_epoll_target use fget_task
Use the helper fget_task and simplify the code. As well as simplifying the code this removes one unnecessary increment of struct files_struct. This unnecessary increment of files_struct.count can result in exec unnecessarily unsharing files_struct and breaking posix locks, and it can result in fget_light having to fallback to fget reducing performance. Suggested-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Cyrill Gorcunov <gorcunov@gmail.com> v1: https://lkml.kernel.org/r/20200817220425.9389-4-ebiederm@xmission.com Link: https://lkml.kernel.org/r/20201120231441.29911-4-ebiederm@xmission.com Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Diffstat (limited to 'kernel/kcmp.c')
-rw-r--r--kernel/kcmp.c20
1 files changed, 4 insertions, 16 deletions
diff --git a/kernel/kcmp.c b/kernel/kcmp.c
index b3ff9288c6cc..87c48c0104ad 100644
--- a/kernel/kcmp.c
+++ b/kernel/kcmp.c
@@ -107,7 +107,6 @@ static int kcmp_epoll_target(struct task_struct *task1,
{
struct file *filp, *filp_epoll, *filp_tgt;
struct kcmp_epoll_slot slot;
- struct files_struct *files;
if (copy_from_user(&slot, uslot, sizeof(slot)))
return -EFAULT;
@@ -116,23 +115,12 @@ static int kcmp_epoll_target(struct task_struct *task1,
if (!filp)
return -EBADF;
- files = get_files_struct(task2);
- if (!files)
+ filp_epoll = fget_task(task2, slot.efd);
+ if (!filp_epoll)
return -EBADF;
- spin_lock(&files->file_lock);
- filp_epoll = fcheck_files(files, slot.efd);
- if (filp_epoll)
- get_file(filp_epoll);
- else
- filp_tgt = ERR_PTR(-EBADF);
- spin_unlock(&files->file_lock);
- put_files_struct(files);
-
- if (filp_epoll) {
- filp_tgt = get_epoll_tfile_raw_ptr(filp_epoll, slot.tfd, slot.toff);
- fput(filp_epoll);
- }
+ filp_tgt = get_epoll_tfile_raw_ptr(filp_epoll, slot.tfd, slot.toff);
+ fput(filp_epoll);
if (IS_ERR(filp_tgt))
return PTR_ERR(filp_tgt);