+ proc-proc_maps_open-allow-proc_mem_open-to-return-null.patch added to mm-hotfixes-unstable branch

+ proc-proc_maps_open-allow-proc_mem_open-to-return-null.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: proc: proc_maps_open allow proc_mem_open to return NULL
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     proc-proc_maps_open-allow-proc_mem_open-to-return-null.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/proc-proc_maps_open-allow-proc_mem_open-to-return-null.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Jialin Wang <wjl.linux@gmail.com>
Subject: proc: proc_maps_open allow proc_mem_open to return NULL
Date: Fri, 8 Aug 2025 00:54:55 +0800

commit 65c66047259f ("proc: fix the issue of proc_mem_open returning
NULL") breaks `perf record -g -p PID` when profiling a kernel thread.

The strace of `perf record -g -p $(pgrep kswapd0)` shows:

  openat(AT_FDCWD, "/proc/65/task/65/maps", O_RDONLY) = -1 ESRCH (No such process)

This patch partially reverts the commit to fix it.

Link: https://lkml.kernel.org/r/20250807165455.73656-1-wjl.linux@gmail.com
Fixes: 65c66047259f ("proc: fix the issue of proc_mem_open returning NULL")
Signed-off-by: Jialin Wang <wjl.linux@gmail.com>
Cc: Penglei Jiang <superman.xpt@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/task_mmu.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/proc/task_mmu.c~proc-proc_maps_open-allow-proc_mem_open-to-return-null
+++ a/fs/proc/task_mmu.c
@@ -340,8 +340,8 @@ static int proc_maps_open(struct inode *
 
 	priv->inode = inode;
 	priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
-	if (IS_ERR_OR_NULL(priv->mm)) {
-		int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
+	if (IS_ERR(priv->mm)) {
+		int err = PTR_ERR(priv->mm);
 
 		seq_release_private(inode, file);
 		return err;
_

Patches currently in -mm which might be from wjl.linux@gmail.com are

proc-proc_maps_open-allow-proc_mem_open-to-return-null.patch