linux-kernel - [PATCH AUTOSEL 4.19 07/68] xsk: fix umem memory leak on cleanup

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Date:   Mon, 22 Apr 2019 15:44:15 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org,
        xdp-newbies@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 07/68] xsk: fix umem memory leak on cleanup

From: Björn Töpel <bjorn.topel@...el.com>

[ Upstream commit 044175a06706d516aa42874bb44dbbfc3c4d20eb ]

When the umem is cleaned up, the task that created it might already be
gone. If the task was gone, the xdp_umem_release function did not free
the pages member of struct xdp_umem.

It turned out that the task lookup was not needed at all; The code was
a left-over when we moved from task accounting to user accounting [1].

This patch fixes the memory leak by removing the task lookup logic
completely.

[1] https://lore.kernel.org/netdev/20180131135356.19134-3-bjorn.topel@gmail.com/

Link: https://lore.kernel.org/netdev/c1cb2ca8-6a14-3980-8672-f3de0bb38dfd@suse.cz/
Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt")
Reported-by: Jiri Slaby <jslaby@...e.cz>
Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Sasha Levin (Microsoft) <sashal@...nel.org>
---
 include/net/xdp_sock.h |  1 -
 net/xdp/xdp_umem.c     | 19 +------------------
 2 files changed, 1 insertion(+), 19 deletions(-)

diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index 7161856bcf9c..c2c10cc9ffa0 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -34,7 +34,6 @@ struct xdp_umem {
 	u32 headroom;
 	u32 chunk_size_nohr;
 	struct user_struct *user;
-	struct pid *pid;
 	unsigned long address;
 	refcount_t users;
 	struct work_struct work;
diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index bfe2dbea480b..a3b037fbfecd 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -152,9 +152,6 @@ static void xdp_umem_unaccount_pages(struct xdp_umem *umem)
 
 static void xdp_umem_release(struct xdp_umem *umem)
 {
-	struct task_struct *task;
-	struct mm_struct *mm;
-
 	xdp_umem_clear_dev(umem);
 
 	if (umem->fq) {
@@ -169,21 +166,10 @@ static void xdp_umem_release(struct xdp_umem *umem)
 
 	xdp_umem_unpin_pages(umem);
 
-	task = get_pid_task(umem->pid, PIDTYPE_PID);
-	put_pid(umem->pid);
-	if (!task)
-		goto out;
-	mm = get_task_mm(task);
-	put_task_struct(task);
-	if (!mm)
-		goto out;
-
-	mmput(mm);
 	kfree(umem->pages);
 	umem->pages = NULL;
 
 	xdp_umem_unaccount_pages(umem);
-out:
 	kfree(umem);
 }
 
@@ -312,7 +298,6 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 	if (size_chk < 0)
 		return -EINVAL;
 
-	umem->pid = get_task_pid(current, PIDTYPE_PID);
 	umem->address = (unsigned long)addr;
 	umem->props.chunk_mask = ~((u64)chunk_size - 1);
 	umem->props.size = size;
@@ -328,7 +313,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 
 	err = xdp_umem_account_pages(umem);
 	if (err)
-		goto out;
+		return err;
 
 	err = xdp_umem_pin_pages(umem);
 	if (err)
@@ -347,8 +332,6 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 
 out_account:
 	xdp_umem_unaccount_pages(umem);
-out:
-	put_pid(umem->pid);
 	return err;
 }
 
-- 
2.19.1