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h=Date:From:To:Subject:From; b=qeXkitTI/7GFZ2FApdi/I9o2ZxgaYoH70FCsBLOH1baRAqKZKT7+0gwEb0YLGT4jI KVXvUQsuijo6ZQDDenaXV1aFp9vyh4opM66OZHNTpFVXpVfsp1dz7A3PkV876OdpTK Eq1Hzt4tQbnHFbge0rSoc+I1o4kiXVT1VMsu4TT7lzPR/gIgJfYupST+09bOaP8VVu UaqTfsplSnlRy03yOV4RxeRMlzG2OIdnTbeqFVp48OxJe0jwhUL52fGrRZvEi2eSwn IquOzirA5eC0Z5C3NZugT6DG3cMGM5y2ZoqrZQypefYJlYOqrVCw8bzWxm0LkFYJg/ JwIhhHATc1dbw== Date: Sat, 1 Feb 2025 20:51:27 +0000 From: Nir Lichtman To: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, kees@kernel.org, ebiederm@xmission.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH] exec: improve clarity of comment regarding pid save-asides Message-ID: <20250201205127.GA1191798@lichtman.org> MIME-Version: 1.0 Content-Disposition: inline X-Stat-Signature: yhmsqyuc1ng6qpk53igjp1waw894wrm4 X-Rspam-User: X-Rspamd-Queue-Id: 77A281A0006 X-Rspamd-Server: rspam03 X-HE-Tag: 1738443088-531077 X-HE-Meta: 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 7CTzqyg0 QGm8gQj/maPPMP0a9aS53bNF1gkLuywBSX6nmwDPOVSIHaEfCDT4wLct/8jtyjT8nD7vGVAKy5LhiDKWeF9XjLm5IxiurAYacTXu4PF2hx5DD306x4GDtds7IjCxZ8XrFjRyhoWIh3Z0sLGprChJDtP8c7zntsBmm2UPEnK7sbxmF4Jlg44dLsGiL2TDLiN+9oD5+6JFTZhG2tWf4aCw/DD0KZJOy3pGBhMBUxjARp0zIEfTrZu64tWbDfgJNF7+fSAEcrN4SdoFm6GA3oEXLcbGH24SHDidnO8AXMVbu2Gz/MQI= 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: Problem: Current comment regarding saving aside the old pid and old vpid is very vague, especially when considering that it is unexpected that execve can actually kill the current process. Solution: Improve the description of the comment explaining more in-depth the reasoning behind. Suggested-by: Kees Cook Signed-off-by: Nir Lichtman --- fs/exec.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/exec.c b/fs/exec.c index 506cd411f4ac..343c435b00ee 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1792,7 +1792,14 @@ static int exec_binprm(struct linux_binprm *bprm) pid_t old_pid, old_vpid; int ret, depth; - /* Need to fetch pid before load_binary changes it */ + /* + * Need to save aside the current thread pid and vpid + * since if the current thread is not a thread group leader + * the logic in de_thread kills the current thread and all + * other threads in the current thread group, except the leader. + * The new program will execute in the leader, with the leader pid + * ("man 2 clone" CLONE_THREAD flag for more info) + */ old_pid = current->pid; rcu_read_lock(); old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));