Re: [PATCH 1/5] kernel: replace sizeof(task->comm) with TASK_COMM_LEN

From: Yafang Shao
Date: Thu Sep 30 2021 - 08:27:47 EST

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In reply to: Kees Cook: "Re: [PATCH 1/5] kernel: replace sizeof(task->comm) with TASK_COMM_LEN"
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On Thu, Sep 30, 2021 at 2:09 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>
> On Wed, Sep 29, 2021 at 11:50:32AM +0000, Yafang Shao wrote:
> > We can use TASK_COMM_LEN directly instread of sizeof(task->comm).
>
> This change makes sense if we accept performing allocation for
> task->comm, but I don't think that's a good idea. I'll reply to those
> patches...
>

Thanks for the review.

> > This patch also replace strlcpy with strscpy, to fix the warning by
> > checkpatch -
> > WARNING: Prefer strscpy over strlcpy - see: https://lore.kernel.org/r/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@xxxxxxxxxxxxxx/
>
> I like this part of the patch, though! :)
>

I will make it a separate patch.

>
> >
> > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> > ---
> > arch/ia64/kernel/mca.c | 6 +++---
> > drivers/block/drbd/drbd_main.c | 2 +-
> > drivers/hwtracing/stm/core.c | 2 +-
> > drivers/tty/tty_audit.c | 2 +-
> > fs/exec.c | 2 +-
> > kernel/audit.c | 4 ++--
> > kernel/auditsc.c | 4 ++--
> > kernel/capability.c | 4 ++--
> > kernel/futex.c | 2 +-
> > kernel/sys.c | 2 +-
> > kernel/trace/blktrace.c | 2 +-
> > security/lsm_audit.c | 4 ++--
> > security/selinux/selinuxfs.c | 2 +-
> > security/yama/yama_lsm.c | 2 +-
> > sound/core/oss/pcm_oss.c | 2 +-
> > 15 files changed, 21 insertions(+), 21 deletions(-)
> >
> > diff --git a/arch/ia64/kernel/mca.c b/arch/ia64/kernel/mca.c
> > index e628a88607bb..4ee86e91ff5e 100644
> > --- a/arch/ia64/kernel/mca.c
> > +++ b/arch/ia64/kernel/mca.c
> > @@ -875,7 +875,7 @@ copy_reg(const u64 *fr, u64 fnat, unsigned long *tr, unsigned long *tnat)
> > static void
> > ia64_mca_modify_comm(const struct task_struct *previous_current)
> > {
> > - char *p, comm[sizeof(current->comm)];
> > + char *p, comm[TASK_COMM_LEN];
> > if (previous_current->pid)
> > snprintf(comm, sizeof(comm), "%s %d",
> > current->comm, previous_current->pid);
> > @@ -889,7 +889,7 @@ ia64_mca_modify_comm(const struct task_struct *previous_current)
> > current->comm, l, previous_current->comm,
> > task_thread_info(previous_current)->cpu);
> > }
> > - memcpy(current->comm, comm, sizeof(current->comm));
> > + memcpy(current->comm, comm, TASK_COMM_LEN);
> > }
> >
> > static void
> > @@ -1794,7 +1794,7 @@ format_mca_init_stack(void *mca_data, unsigned long offset,
> > p->parent = p->real_parent = p->group_leader = p;
> > INIT_LIST_HEAD(&p->children);
> > INIT_LIST_HEAD(&p->sibling);
> > - strncpy(p->comm, type, sizeof(p->comm)-1);
> > + strncpy(p->comm, type, TASK_COMM_LEN-1);
> > }
> >
> > /* Caller prevents this from being called after init */
> > diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
> > index 55234a558e98..a7cf062e76ab 100644
> > --- a/drivers/block/drbd/drbd_main.c
> > +++ b/drivers/block/drbd/drbd_main.c
> > @@ -306,7 +306,7 @@ static int drbd_thread_setup(void *arg)
> > unsigned long flags;
> > int retval;
> >
> > - snprintf(current->comm, sizeof(current->comm), "drbd_%c_%s",
> > + snprintf(current->comm, TASK_COMM_LEN, "drbd_%c_%s",
> > thi->name[0],
> > resource->name);
> >
> > diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
> > index 2712e699ba08..8ec0a34a9ba6 100644
> > --- a/drivers/hwtracing/stm/core.c
> > +++ b/drivers/hwtracing/stm/core.c
> > @@ -631,7 +631,7 @@ static ssize_t stm_char_write(struct file *file, const char __user *buf,
> > * point, try to use the task name and "default" policy entries.
> > */
> > if (!stmf->output.nr_chans) {
> > - char comm[sizeof(current->comm)];
> > + char comm[TASK_COMM_LEN];
> > char *ids[] = { comm, "default", NULL };
> >
> > get_task_comm(comm, current);
> > diff --git a/drivers/tty/tty_audit.c b/drivers/tty/tty_audit.c
> > index ca7afd7b2716..b98b1aef5f6f 100644
> > --- a/drivers/tty/tty_audit.c
> > +++ b/drivers/tty/tty_audit.c
> > @@ -69,7 +69,7 @@ static void tty_audit_log(const char *description, dev_t dev,
> >
> > ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TTY);
> > if (ab) {
> > - char name[sizeof(current->comm)];
> > + char name[TASK_COMM_LEN];
> >
> > audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d"
> > " minor=%d comm=", description, pid, uid,
> > diff --git a/fs/exec.c b/fs/exec.c
> > index a098c133d8d7..021c9dc727bc 100644
> > --- a/fs/exec.c
> > +++ b/fs/exec.c
> > @@ -1224,7 +1224,7 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
> > {
> > task_lock(tsk);
> > trace_task_rename(tsk, buf);
> > - strlcpy(tsk->comm, buf, sizeof(tsk->comm));
> > + strscpy(tsk->comm, buf, TASK_COMM_LEN);
> > task_unlock(tsk);
> > perf_event_comm(tsk, exec);
> > }
> > diff --git a/kernel/audit.c b/kernel/audit.c
> > index 121d37e700a6..1fbd036e77be 100644
> > --- a/kernel/audit.c
> > +++ b/kernel/audit.c
> > @@ -1549,7 +1549,7 @@ static void audit_log_multicast(int group, const char *op, int err)
> > {
> > const struct cred *cred;
> > struct tty_struct *tty;
> > - char comm[sizeof(current->comm)];
> > + char comm[TASK_COMM_LEN];
> > struct audit_buffer *ab;
> >
> > if (!audit_enabled)
> > @@ -2192,7 +2192,7 @@ void audit_put_tty(struct tty_struct *tty)
> > void audit_log_task_info(struct audit_buffer *ab)
> > {
> > const struct cred *cred;
> > - char comm[sizeof(current->comm)];
> > + char comm[TASK_COMM_LEN];
> > struct tty_struct *tty;
> >
> > if (!ab)
> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > index 8dd73a64f921..295376d7d926 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -2595,7 +2595,7 @@ void __audit_log_nfcfg(const char *name, u8 af, unsigned int nentries,
> > enum audit_nfcfgop op, gfp_t gfp)
> > {
> > struct audit_buffer *ab;
> > - char comm[sizeof(current->comm)];
> > + char comm[TASK_COMM_LEN];
> >
> > ab = audit_log_start(audit_context(), gfp, AUDIT_NETFILTER_CFG);
> > if (!ab)
> > @@ -2616,7 +2616,7 @@ static void audit_log_task(struct audit_buffer *ab)
> > kuid_t auid, uid;
> > kgid_t gid;
> > unsigned int sessionid;
> > - char comm[sizeof(current->comm)];
> > + char comm[TASK_COMM_LEN];
> >
> > auid = audit_get_loginuid(current);
> > sessionid = audit_get_sessionid(current);
> > diff --git a/kernel/capability.c b/kernel/capability.c
> > index 46a361dde042..4033ee837f63 100644
> > --- a/kernel/capability.c
> > +++ b/kernel/capability.c
> > @@ -45,7 +45,7 @@ __setup("no_file_caps", file_caps_disable);
> >
> > static void warn_legacy_capability_use(void)
> > {
> > - char name[sizeof(current->comm)];
> > + char name[TASK_COMM_LEN];
> >
> > pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n",
> > get_task_comm(name, current));
> > @@ -69,7 +69,7 @@ static void warn_legacy_capability_use(void)
> >
> > static void warn_deprecated_v2(void)
> > {
> > - char name[sizeof(current->comm)];
> > + char name[TASK_COMM_LEN];
> >
> > pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n",
> > get_task_comm(name, current));
> > diff --git a/kernel/futex.c b/kernel/futex.c
> > index c15ad276fd15..6cd08156611e 100644
> > --- a/kernel/futex.c
> > +++ b/kernel/futex.c
> > @@ -1703,7 +1703,7 @@ static int futex_atomic_op_inuser(unsigned int encoded_op, u32 __user *uaddr)
> >
> > if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28)) {
> > if (oparg < 0 || oparg > 31) {
> > - char comm[sizeof(current->comm)];
> > + char comm[TASK_COMM_LEN];
> > /*
> > * kill this print and return -EINVAL when userspace
> > * is sane again
> > diff --git a/kernel/sys.c b/kernel/sys.c
> > index 8fdac0d90504..bea1120c5579 100644
> > --- a/kernel/sys.c
> > +++ b/kernel/sys.c
> > @@ -2265,7 +2265,7 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
> > unsigned long, arg4, unsigned long, arg5)
> > {
> > struct task_struct *me = current;
> > - unsigned char comm[sizeof(me->comm)];
> > + unsigned char comm[TASK_COMM_LEN];
> > long error;
> >
> > error = security_task_prctl(option, arg2, arg3, arg4, arg5);
> > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> > index c221e4c3f625..009f77ebda5a 100644
> > --- a/kernel/trace/blktrace.c
> > +++ b/kernel/trace/blktrace.c
> > @@ -124,7 +124,7 @@ static void trace_note_tsk(struct task_struct *tsk)
> > spin_lock_irqsave(&running_trace_lock, flags);
> > list_for_each_entry(bt, &running_trace_list, running_list) {
> > trace_note(bt, tsk->pid, BLK_TN_PROCESS, tsk->comm,
> > - sizeof(tsk->comm), 0);
> > + TASK_COMM_LEN, 0);
> > }
> > spin_unlock_irqrestore(&running_trace_lock, flags);
> > }
> > diff --git a/security/lsm_audit.c b/security/lsm_audit.c
> > index 5a5016ef43b0..eec54cb48845 100644
> > --- a/security/lsm_audit.c
> > +++ b/security/lsm_audit.c
> > @@ -208,7 +208,7 @@ static inline void print_ipv4_addr(struct audit_buffer *ab, __be32 addr,
> > static void dump_common_audit_data(struct audit_buffer *ab,
> > struct common_audit_data *a)
> > {
> > - char comm[sizeof(current->comm)];
> > + char comm[TASK_COMM_LEN];
> >
> > /*
> > * To keep stack sizes in check force programers to notice if they
> > @@ -310,7 +310,7 @@ static void dump_common_audit_data(struct audit_buffer *ab,
> > if (tsk) {
> > pid_t pid = task_tgid_nr(tsk);
> > if (pid) {
> > - char comm[sizeof(tsk->comm)];
> > + char comm[TASK_COMM_LEN];
> > audit_log_format(ab, " opid=%d ocomm=", pid);
> > audit_log_untrustedstring(ab,
> > memcpy(comm, tsk->comm, sizeof(comm)));
> > diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
> > index e4cd7cb856f3..e529db76502d 100644
> > --- a/security/selinux/selinuxfs.c
> > +++ b/security/selinux/selinuxfs.c
> > @@ -752,7 +752,7 @@ static ssize_t sel_write_checkreqprot(struct file *file, const char __user *buf,
> > goto out;
> >
> > if (new_value) {
> > - char comm[sizeof(current->comm)];
> > + char comm[TASK_COMM_LEN];
> >
> > memcpy(comm, current->comm, sizeof(comm));
> > pr_warn_once("SELinux: %s (%d) set checkreqprot to 1. This is deprecated and will be rejected in a future kernel release.\n",
> > diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
> > index 06e226166aab..178d7a138e98 100644
> > --- a/security/yama/yama_lsm.c
> > +++ b/security/yama/yama_lsm.c
> > @@ -75,7 +75,7 @@ static void report_access(const char *access, struct task_struct *target,
> > struct task_struct *agent)
> > {
> > struct access_report_info *info;
> > - char agent_comm[sizeof(agent->comm)];
> > + char agent_comm[TASK_COMM_LEN];
> >
> > assert_spin_locked(&target->alloc_lock); /* for target->comm */
> >
> > diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
> > index 82a818734a5f..d541530236e1 100644
> > --- a/sound/core/oss/pcm_oss.c
> > +++ b/sound/core/oss/pcm_oss.c
> > @@ -2460,7 +2460,7 @@ static int snd_task_name(struct task_struct *task, char *name, size_t size)
> >
> > if (snd_BUG_ON(!task || !name || size < 2))
> > return -EINVAL;
> > - for (idx = 0; idx < sizeof(task->comm) && idx + 1 < size; idx++)
> > + for (idx = 0; idx < TASK_COMM_LEN && idx + 1 < size; idx++)
> > name[idx] = task->comm[idx];
> > name[idx] = '\0';
> > return 0;
> > --
> > 2.17.1
> >
>
> --
> Kees Cook

--
Thanks
Yafang

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