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b=FZHk2/+9ACjM7o7Rjf7SP/4O3KHTPhWa5w9B2T12kMqVSLkBY0utwyXfrtOG8GwXD 9E8rjAS7AMjD9jrCjJnOIlDsqeM/Gn5Ku6l5q2+f7Gds9PLHnvmALDW4dY7pLmYsEG bqqxXfI0rlIhnmk5lBxig1yjz/UpwJgOkx64KX83cjKYxK+BSb0ZBhBee6MdL6BfJl +/E5mUb5xx9Uvfe4Bk22+M22elaQwVQEI+64t/VoDTtPAYgJOVaGZQaT6DABLSvAAn 0orxhLjf012TPAs7eySi7/mT8XhpSPN/jD7hYy+2M/Zm1b6qQVj1rT1sb958mf50xB 9g1jgdeYN6MUA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v8 5/6] prctl: Add support for long user thread names Reply-To: sashiko-reviews@lists.linux.dev To: =?utf-8?b?QW5kcsOpIEFsbWVpZGE=?= , "Peter Zijlstra" , "Juri Lelli" , "Vincent Guittot" , "Steven Rostedt" , "Christian Brauner" , "Kees Cook" , "Shuah Khan" , willy@infradead.org, mathieu.desnoyers@efficios.com, "David Laight" , "Linus Torvalds" , akpm@linux-foundation.org, "Yafang Shao" , andrii.nakryiko@gmail.com, arnaldo.melo@gmail.com, "Petr Mladek" Cc: kernel-dev@igalia.com, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org In-Reply-To: <20261030-tonyk-long_name-v8-5-c9b030332254@igalia.com> References: <20261030-tonyk-long_name-v8-0-c9b030332254@igalia.com> <20261030-tonyk-long_name-v8-5-c9b030332254@igalia.com> Content-Type: text/plain; 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Sashiko AI review found 1 potential issue(= s) to consider: - [Medium] prctl: missing arg validation and buffer size UAPI in PR_{SET,GE= T}_EXT_NAME -- commit d86849bc61de6aa30e004f18202851c2e72d0d41 Author: Andr=C3=A9 Almeida prctl: Add support for long user thread names This commit adds the PR_SET_EXT_NAME and PR_GET_EXT_NAME prctl() options to support getting and setting extended user thread names up to TASK_COMM_EXT_LEN bytes. > diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h > index b6ec6f6937195..a07f8edadd652 100644 > --- a/include/uapi/linux/prctl.h > +++ b/include/uapi/linux/prctl.h > @@ -56,6 +56,9 @@ > #define PR_SET_NAME 15 /* Set process name */ > #define PR_GET_NAME 16 /* Get process name */ > =20 > +#define PR_SET_EXT_NAME 17 /* Set extended process name */ > +#define PR_GET_EXT_NAME 18 /* Get extended process name */ > + > /* Get/set process endian */ > #define PR_GET_ENDIAN 19 > #define PR_SET_ENDIAN 20 > diff --git a/kernel/sys.c b/kernel/sys.c > index 6a72c7e644e70..fc9e3c5a91353 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c [ ... ] > @@ -2616,6 +2616,19 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long,= arg2, unsigned long, arg3, > if (copy_to_user((char __user *)arg2, comm, TASK_COMM_LEN)) > return -EFAULT; > break; > + case PR_SET_EXT_NAME: > + comm[TASK_COMM_EXT_LEN - 1] =3D 0; > + if (strncpy_from_user(comm, (char __user *)arg2, > + TASK_COMM_EXT_LEN - 1) < 0) > + return -EFAULT; > + set_task_comm(me, comm); > + proc_comm_connector(me); > + break; > + case PR_GET_EXT_NAME: > + strscpy_pad(comm, me->comm, TASK_COMM_EXT_LEN); > + if (copy_to_user((char __user *)arg2, comm, TASK_COMM_EXT_LEN)) > + return -EFAULT; > + break; [Severity: Medium] Should PR_SET_EXT_NAME and PR_GET_EXT_NAME in SYSCALL_DEFINE5(prctl) valida= te that the unused arguments (arg3, arg4, and arg5) are zero and return -EINVAL otherwise? Because libc's prctl() wrapper is variadic, 2-argument calls from userspace can pass arbitrary register values in arg3..arg5, which prevents extending these options with flags or length parameters in the future. In addition, PR_GET_EXT_NAME unconditionally copies TASK_COMM_EXT_LEN (64) bytes to the userspace buffer at arg2, but TASK_COMM_EXT_LEN is only defined in include/linux/sched.h and is not exposed in include/uapi/linux/prctl.h: include/linux/sched.h: enum { TASK_COMM_LEN =3D 16, TASK_COMM_EXT_LEN =3D 64, }; Without a UAPI constant or a buffer size argument in PR_GET_EXT_NAME, could= a userspace caller passing a smaller buffer (or passing a buffer length in ar= g3) have 64 bytes written past the end of its buffer, or break if TASK_COMM_EXT_LEN is ever increased? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261030-tonyk-long= _name-v8-0-c9b030332254@igalia.com?part=3D5