[PATCH 2/2] mm: use pidfd_get_task()

From: Christian Brauner
Date: Mon Oct 04 2021 - 08:51:48 EST


Instead of duplicating the same code in two places use the newly added
pidfd_get_task() helper. This fixes an (unimportant for now) bug where
PIDTYPE_PID is used whereas PIDTYPE_TGID should have been used.

Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Matthew Bobrowski <repnop@xxxxxxxxxx>
Cc: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
---
mm/madvise.c | 15 +++------------
mm/oom_kill.c | 15 +++------------
2 files changed, 6 insertions(+), 24 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 0734db8d53a7..8c927202bbe6 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1235,7 +1235,6 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
struct iovec iovstack[UIO_FASTIOV], iovec;
struct iovec *iov = iovstack;
struct iov_iter iter;
- struct pid *pid;
struct task_struct *task;
struct mm_struct *mm;
size_t total_len;
@@ -1250,18 +1249,12 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
if (ret < 0)
goto out;

- pid = pidfd_get_pid(pidfd, &f_flags);
- if (IS_ERR(pid)) {
- ret = PTR_ERR(pid);
+ task = pidfd_get_task(pidfd, &f_flags);
+ if (IS_ERR(task)) {
+ ret = PTR_ERR(task);
goto free_iov;
}

- task = get_pid_task(pid, PIDTYPE_PID);
- if (!task) {
- ret = -ESRCH;
- goto put_pid;
- }
-
if (!process_madvise_behavior_valid(behavior)) {
ret = -EINVAL;
goto release_task;
@@ -1301,8 +1294,6 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
mmput(mm);
release_task:
put_task_struct(task);
-put_pid:
- put_pid(pid);
free_iov:
kfree(iov);
out:
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 831340e7ad8b..70d399d5817e 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -1151,21 +1151,14 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
struct task_struct *p;
unsigned int f_flags;
bool reap = true;
- struct pid *pid;
long ret = 0;

if (flags)
return -EINVAL;

- pid = pidfd_get_pid(pidfd, &f_flags);
- if (IS_ERR(pid))
- return PTR_ERR(pid);
-
- task = get_pid_task(pid, PIDTYPE_TGID);
- if (!task) {
- ret = -ESRCH;
- goto put_pid;
- }
+ task = pidfd_get_task(pidfd, &f_flags);
+ if (IS_ERR(task))
+ return PTR_ERR(task);

/*
* Make sure to choose a thread which still has a reference to mm
@@ -1204,8 +1197,6 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
mmdrop(mm);
put_task:
put_task_struct(task);
-put_pid:
- put_pid(pid);
return ret;
#else
return -ENOSYS;
--
2.30.2