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Fri, 08 Aug 2025 05:53:54 -0700 (PDT) From: Jialin Wang To: akpm@linux-foundation.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, superman.xpt@gmail.com, wjl.linux@gmail.com Subject: [PATCH v2] proc: proc_maps_open allow proc_mem_open to return NULL Date: Fri, 8 Aug 2025 20:53:47 +0800 Message-ID: <20250808125347.14775-1-wjl.linux@gmail.com> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250807154606.131d96b133c19baca0c5f2e6@linux-foundation.org> References: <20250807154606.131d96b133c19baca0c5f2e6@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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//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. Fixes: 65c66047259f ("proc: fix the issue of proc_mem_open returning NULL") Signed-off-by: Jialin Wang --- Changes in v2 (Thanks to Andrew): - Add more detailed misbehavior description in commit message 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 3d6d8a9f13fc..7a7ce26106ac 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; -- 2.50.0