From: Jialin Wang wjl.linux@gmail.com

The commit 65c66047259f ("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: 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(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index ee1e4ccd33bd..29cca0e6d0ff 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -340,8 +340,8 @@ static int proc_maps_open(struct inode *inode, struct file *file,

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;