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proc: proc_maps_open allow proc_mem_open to return NULL

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The commit 65c6604725 ("proc: fix the issue of proc_mem_open returning
NULL") caused proc_maps_open() to return -ESRCH when proc_mem_open()
returns NULL.  This breaks legitimate /proc/<pid>/maps access for kernel
threads since kernel threads have NULL mm_struct.

The regression causes perf to fail and exit when profiling a kernel
thread:

  # perf record -v -g -p $(pgrep kswapd0)
  ...
  couldn't open /proc/65/task/65/maps

This patch partially reverts the commit to fix it.

Link: https://lkml.kernel.org/r/20250807165455.73656-1-wjl.linux@gmail.com
Fixes: 65c6604725 ("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>
This commit is contained in:
Jialin Wang 2025-08-08 00:54:55 +08:00 • committed by Andrew Morton
parent 0b5be138ce
commit c0e1b774f6
1 changed files with 2 additions and 2 deletions
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4
fs/proc/task_mmu.c
View file

@ -340,8 +340,8 @@ static int proc_maps_open(struct inode *inode, struct file *file,
priv->inode = inode; priv->inode = inode;
priv->mm = proc_mem_open(inode, PTRACE_MODE_READ); priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
if (IS_ERR_OR_NULL(priv->mm)) { if (IS_ERR(priv->mm)) {
int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH; int err = PTR_ERR(priv->mm);
seq_release_private(inode, file); seq_release_private(inode, file);
return err; return err;