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b=HHbdSpqhJwpTWDnjBe+rRqKqM7d69+KpBrghiH1jALmo2Ut7w+OVrQL+sNv6Szxi3 326GF/RFWeGbSfojoa1iRmH1e7HVgus6eRaDlrVhBRRIOdPIoAFPatBfvhS92VXWHJ QVH2M8EN7oGslP8w9dE9LQ+RA6ZZOIOWVi1bw4Myr/7hXZYcfFlyNDSBb/rMl4jTKJ DFZ6djxsBIhKMrp3Q6ie8mWWryGtqQUoFHQGOrIltE6/GlBzGUI7f3V3+nvNrMGs6E 9VVwk4rbaMUINBV5HFEwsyIERc35iE2ypjJX4nlkDl/JYa+NmQ3Ds42gw13g64mQMi O2Mar20c9eNBw== Date: Fri, 14 Mar 2025 14:25:09 -0700 From: Kees Cook To: Bhupesh Cc: akpm@linux-foundation.org, 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, 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: Re: [PATCH RFC 0/2] Dynamically allocate memory to store task's full name Message-ID: <202503141420.37D605B2@keescook> References: <20250314052715.610377-1-bhupesh@igalia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250314052715.610377-1-bhupesh@igalia.com> X-Rspamd-Server: rspam07 X-Rspam-User: X-Stat-Signature: cy7j13jhk7q9w1gkprdk5uzh8bc5t6eg X-Rspamd-Queue-Id: BDE351C0006 X-HE-Tag: 1741987513-508253 X-HE-Meta: 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 M6nkEKZQ kcaEJZVORpJx2JzfygnjBV8e+puS7zWHCvHVG2kgZ9ojlvVL62ZrrGM03sdo5nynxSwqhm60uU32iLJXUPtf1OpPKPTBzOqG+Br2HemsOmvdh4ST4oTyst57Re1koaAUSracnXNZVFa8qnjGEiZflvoplMY4VrC1u26kw8x4yM1wpy5PCnVTnGwbnyk21EWLv/+HiNRsp2RKgMgTk7ilOCf3MXU/hp66GQKvC3lwudSmuYHWM3bbrhCdCkxy5i0j4NOK+F3TYMKkARl59Sxr+KIcnF8mJ0dvfPOwUvXPB1m0xc+hwO/oFUP+kk7M7Smo3QLzu 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: On Fri, Mar 14, 2025 at 10:57:13AM +0530, Bhupesh wrote: > While working with user-space debugging tools which work especially > on linux gaming platforms, I found that the task name is truncated due > to the limitation of TASK_COMM_LEN. > > For example, currently running 'ps', the task->comm value of a long > task name is truncated due to the limitation of TASK_COMM_LEN. > create_very_lon > > This leads to the names passed from userland via pthread_setname_np() > being truncated. So there have been long discussions about "comm", and it mainly boils down to "leave it alone". For the /proc-scraping tools like "ps" and "top", they check both "comm" and "cmdline", depending on mode. The more useful (and already untruncated) stuff is in "cmdline", so I suspect it may make more sense to have pthread_setname_np() interact with that instead. Also TASK_COMM_LEN is basically considered userspace ABI at this point and we can't sanely change its length without breaking the world. Best to use /proc/$pid/task/$tid/cmdline IMO... -Kees > will be shown in 'ps'. For example: > create_very_long_name_user_space_script.sh > > Bhupesh (2): > exec: Dynamically allocate memory to store task's full name > fs/proc: Pass 'task->full_name' via 'proc_task_name()' > > fs/exec.c | 21 ++++++++++++++++++--- > fs/proc/array.c | 2 +- > include/linux/sched.h | 9 +++++++++ > 3 files changed, 28 insertions(+), 4 deletions(-) > > -- > 2.38.1 > -- Kees Cook