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b=gw4iRTuDAS2eJw3qoVdsWlnm85 8tZt4oDOh/smHkqLc+e8A+qD4PWm7Cactc053/Q3Z2dj9uNTA9HbG+kiOwG7eaAIBdfvC4Kpt18Il 21gVLowHmhQa53uCPwCvDte12WhV5MXah3REGmGfdzOMDJnnyI4wTHouxAIr7s8LYNaDNYdMzhljt hU7fQM1x+XmvqhlgZzIYABZLZTLu7auQX72Z9Lv+jiaxoDfc5GxvqTw27NZTp7ZJjVLFGZfoJnQJS mMoUGf0RhFXJbjHNrO26njrPfwpPKSvdftcuIy8GHlDk8hRUyGvoAbFbuM0g/BmDJdS7yQkrmwH9a a1xutSsg==; Received: from [223.233.77.29] (helo=localhost.localdomain) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1tsxZy-008TWs-Hk; Fri, 14 Mar 2025 06:27:36 +0100 From: Bhupesh To: akpm@linux-foundation.org Cc: bhupesh@igalia.com, kernel-dev@igalia.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, oliver.sang@intel.com, lkp@intel.com, laoar.shao@gmail.com, pmladek@suse.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, arnaldo.melo@gmail.com, alexei.starovoitov@gmail.com, andrii.nakryiko@gmail.com, mirq-linux@rere.qmqm.pl, peterz@infradead.org, willy@infradead.org, david@redhat.com, viro@zeniv.linux.org.uk, keescook@chromium.org, ebiederm@xmission.com, brauner@kernel.org, jack@suse.cz, mingo@redhat.com, juri.lelli@redhat.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com Subject: [PATCH RFC 1/2] exec: Dynamically allocate memory to store task's full name Date: Fri, 14 Mar 2025 10:57:14 +0530 Message-Id: <20250314052715.610377-2-bhupesh@igalia.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20250314052715.610377-1-bhupesh@igalia.com> References: <20250314052715.610377-1-bhupesh@igalia.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam07 X-Rspam-User: X-Stat-Signature: buuyn7o8jef7k1r4nrtms8wqhuwawoba X-Rspamd-Queue-Id: 0BA401C0005 X-HE-Tag: 1741930062-686921 X-HE-Meta: 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 ba4695Xn W7SXmn3QzzY90bIiQm7hK0aslwUljvmEfVTu52K3vp8ox9Zcpg4PB/OsVlaBibjTfu6gYcUCqX84NHmb8FcaEULhRrPe6TKDj6CaJb6KEJK5oMKF9ojXqVKiSBnufAifkiJ5e6s0t+PwMKbItch8gkX2y1/ndXvGkgotCEOq/+ZQR7/LiNe7XvPAMgEB2VE6FfU9npnAC1ehr5RczPiR93U9dmONpoMwoQyE21raGFLuaDe0lVgfiPva+A7BMkwQyjg+8oGKqrjeAX73itt/P14xkuko4QAl2+F8DpmrDjR6YyYpc4DdYGWAGDEeg5LBy7D4jEt3vPZ/IBdM8oRr9lY0XLQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Provide a parallel implementation for get_task_comm() called get_task_full_name() which allows the dynamically allocated and filled-in task's full name to be passed to interested users such as 'ps'. Currently while running 'ps', the 'task->comm' value of a long task name is truncated due to the limitation of TASK_COMM_LEN. For example: # ./create_very_long_name_user_space_script.sh& # ps PID TTY TIME CMD 332 ttyAMA0 00:00:00 create_very_lon This leads to the names passed from userland via 'pthread_setname_np()' being truncated. Now, during debug tracing, seeing truncated names is not very useful. (for example for debug applications invoking 'pthread_getname_np()') to debug task names. One possible way to fix this issue is extending the task comm size, but as 'task->comm' is used in lots of places, that may cause some potential buffer overflows. Another more conservative approach is introducing a new pointer to store task's full name, which won't introduce too much overhead as it is in the non-critical path. After this change, the full name of these truncated tasks will be shown in 'ps'. For example: # ps PID TTY TIME CMD 305 ttyAMA0 00:00:00 create_very_long_name_user_space_script.sh Here is the proposed flow now: 1. 'pthread_setname_np()' like userspace API sets thread name. 2. This will set 'task->full_name' in addition to default 16-byte truncated 'task->comm'. 3. And 'pthread_getname_np()' will retrieve 'task->full_name' by default from the same '/proc/self/task/[tid]/full_name' Step 3 implementation is achieved via the subsequent patch in this patchset. Signed-off-by: Bhupesh --- fs/exec.c | 21 ++++++++++++++++++--- include/linux/sched.h | 9 +++++++++ 2 files changed, 27 insertions(+), 3 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 506cd411f4ac2..43d0a0d81d44e 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1210,6 +1210,9 @@ int begin_new_exec(struct linux_binprm * bprm) { struct task_struct *me = current; int retval; + va_list args; + char *name; + const char *fmt; /* Once we are committed compute the creds */ retval = bprm_creds_from_file(bprm); @@ -1350,11 +1353,22 @@ int begin_new_exec(struct linux_binprm * bprm) * detecting a concurrent rename and just want a terminated name. */ rcu_read_lock(); - __set_task_comm(me, smp_load_acquire(&bprm->file->f_path.dentry->d_name.name), - true); + fmt = smp_load_acquire(&bprm->file->f_path.dentry->d_name.name); + name = kvasprintf(GFP_KERNEL, fmt, args); + if (!name) + return -ENOMEM; + + me->full_name = name; + __set_task_comm(me, fmt, true); rcu_read_unlock(); } else { - __set_task_comm(me, kbasename(bprm->filename), true); + fmt = kbasename(bprm->filename); + name = kvasprintf(GFP_KERNEL, fmt, args); + if (!name) + return -ENOMEM; + + me->full_name = name; + __set_task_comm(me, fmt, true); } /* An exec changes our domain. We are no longer part of the thread @@ -1401,6 +1415,7 @@ int begin_new_exec(struct linux_binprm * bprm) return 0; out_unlock: + kfree(me->full_name); up_write(&me->signal->exec_update_lock); if (!bprm->cred) mutex_unlock(&me->signal->cred_guard_mutex); diff --git a/include/linux/sched.h b/include/linux/sched.h index 9c15365a30c08..ebf121768d951 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1144,6 +1144,9 @@ struct task_struct { */ char comm[TASK_COMM_LEN]; + /* To store the full name if task comm is truncated. */ + char *full_name; + struct nameidata *nameidata; #ifdef CONFIG_SYSVIPC @@ -1984,6 +1987,12 @@ extern void __set_task_comm(struct task_struct *tsk, const char *from, bool exec buf; \ }) +#define get_task_full_name(buf, buf_size, tsk) ({ \ + BUILD_BUG_ON(sizeof(buf) < TASK_COMM_LEN); \ + strscpy_pad(buf, (tsk)->full_name, buf_size); \ + buf; \ +}) + #ifdef CONFIG_SMP static __always_inline void scheduler_ipi(void) { -- 2.38.1