6.12-stable review patch. If anyone has any objections, please let me know.
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From: Jialin Wang wjl.linux@gmail.com
commit c0e1b774f68bdbea1618e356e30672c7f1e32509 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/proc/task_mmu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -212,8 +212,8 @@ 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;