[PATCH v5 2/3] treewide: Switch memcpy() users of 'task->comm' to a more safer implementation

[Bhupesh]

As Linus mentioned in [1], currently we have several memcpy() use-cases
which use 'current->comm' to copy the task name over to local copies.
For an example:

 ...
 char comm[TASK_COMM_LEN];
 memcpy(comm, current->comm, TASK_COMM_LEN);
 ...

These should be modified so that we can later implement approaches
to handle the task->comm's 16-byte length limitation (TASK_COMM_LEN)
in a more modular way (follow-up patch does the same):

 ...
 char comm[TASK_COMM_LEN];
 memcpy(comm, current->comm, TASK_COMM_LEN);
 comm[TASK_COMM_LEN - 1] = '\0';
 ...

The relevant 'memcpy()' users were identified using the following search
pattern:
 $ git grep 'memcpy.*->comm\>'

[1]. https://lore.kernel.org/all/CAHk-=wjAmmHUg6vho1KjzQi2=psR30+CogFd4aXrThr2gsiS4g@xxxxxxxxxxxxxx/

Signed-off-by: Bhupesh <bhupesh@xxxxxxxxxx>
---
 include/linux/coredump.h       | 3 ++-
 include/trace/events/block.h   | 5 +++++
 include/trace/events/oom.h     | 1 +
 include/trace/events/osnoise.h | 1 +
 include/trace/events/signal.h  | 1 +
 include/trace/events/task.h    | 2 ++
 6 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/include/linux/coredump.h b/include/linux/coredump.h
index 68861da4cf7c..988b233dcc09 100644
--- a/include/linux/coredump.h
+++ b/include/linux/coredump.h
@@ -54,7 +54,8 @@ extern void vfs_coredump(const kernel_siginfo_t *siginfo);
 	do {	\
 		char comm[TASK_COMM_LEN];	\
 		/* This will always be NUL terminated. */ \
-		memcpy(comm, current->comm, sizeof(comm)); \
+		memcpy(comm, current->comm, TASK_COMM_LEN); \
+		comm[TASK_COMM_LEN - 1] = '\0'; \
 		printk_ratelimited(Level "coredump: %d(%*pE): " Format "\n",	\
 			task_tgid_vnr(current), (int)strlen(comm), comm, ##__VA_ARGS__);	\
 	} while (0)	\
diff --git a/include/trace/events/block.h b/include/trace/events/block.h
index 3e582d5e3a57..af40096a7114 100644
--- a/include/trace/events/block.h
+++ b/include/trace/events/block.h
@@ -214,6 +214,7 @@ DECLARE_EVENT_CLASS(block_rq,
 		blk_fill_rwbs(__entry->rwbs, rq->cmd_flags);
 		__get_str(cmd)[0] = '\0';
 		memcpy(__entry->comm, current->comm, TASK_COMM_LEN);
+		__entry->comm[TASK_COMM_LEN - 1] = '\0';
 	),
 
 	TP_printk("%d,%d %s %u (%s) %llu + %u %s,%u,%u [%s]",
@@ -352,6 +353,7 @@ DECLARE_EVENT_CLASS(block_bio,
 		__entry->nr_sector	= bio_sectors(bio);
 		blk_fill_rwbs(__entry->rwbs, bio->bi_opf);
 		memcpy(__entry->comm, current->comm, TASK_COMM_LEN);
+		__entry->comm[TASK_COMM_LEN - 1] = '\0';
 	),
 
 	TP_printk("%d,%d %s %llu + %u [%s]",
@@ -435,6 +437,7 @@ TRACE_EVENT(block_plug,
 
 	TP_fast_assign(
 		memcpy(__entry->comm, current->comm, TASK_COMM_LEN);
+		__entry->comm[TASK_COMM_LEN - 1] = '\0';
 	),
 
 	TP_printk("[%s]", __entry->comm)
@@ -454,6 +457,7 @@ DECLARE_EVENT_CLASS(block_unplug,
 	TP_fast_assign(
 		__entry->nr_rq = depth;
 		memcpy(__entry->comm, current->comm, TASK_COMM_LEN);
+		__entry->comm[TASK_COMM_LEN - 1] = '\0';
 	),
 
 	TP_printk("[%s] %d", __entry->comm, __entry->nr_rq)
@@ -505,6 +509,7 @@ TRACE_EVENT(block_split,
 		__entry->new_sector	= new_sector;
 		blk_fill_rwbs(__entry->rwbs, bio->bi_opf);
 		memcpy(__entry->comm, current->comm, TASK_COMM_LEN);
+		__entry->comm[TASK_COMM_LEN - 1] = '\0';
 	),
 
 	TP_printk("%d,%d %s %llu / %llu [%s]",
diff --git a/include/trace/events/oom.h b/include/trace/events/oom.h
index 9f0a5d1482c4..a5641ed4285f 100644
--- a/include/trace/events/oom.h
+++ b/include/trace/events/oom.h
@@ -24,6 +24,7 @@ TRACE_EVENT(oom_score_adj_update,
 	TP_fast_assign(
 		__entry->pid = task->pid;
 		memcpy(__entry->comm, task->comm, TASK_COMM_LEN);
+		__entry->comm[TASK_COMM_LEN - 1] = '\0';
 		__entry->oom_score_adj = task->signal->oom_score_adj;
 	),
 
diff --git a/include/trace/events/osnoise.h b/include/trace/events/osnoise.h
index 3f4273623801..0321b3f8d532 100644
--- a/include/trace/events/osnoise.h
+++ b/include/trace/events/osnoise.h
@@ -117,6 +117,7 @@ TRACE_EVENT(thread_noise,
 
 	TP_fast_assign(
 		memcpy(__entry->comm, t->comm, TASK_COMM_LEN);
+		__entry->comm[TASK_COMM_LEN - 1] = '\0';
 		__entry->pid = t->pid;
 		__entry->start = start;
 		__entry->duration = duration;
diff --git a/include/trace/events/signal.h b/include/trace/events/signal.h
index 1db7e4b07c01..7f490e553db5 100644
--- a/include/trace/events/signal.h
+++ b/include/trace/events/signal.h
@@ -68,6 +68,7 @@ TRACE_EVENT(signal_generate,
 		__entry->sig	= sig;
 		TP_STORE_SIGINFO(__entry, info);
 		memcpy(__entry->comm, task->comm, TASK_COMM_LEN);
+		__entry->comm[TASK_COMM_LEN - 1] = '\0';
 		__entry->pid	= task->pid;
 		__entry->group	= group;
 		__entry->result	= result;
diff --git a/include/trace/events/task.h b/include/trace/events/task.h
index af535b053033..4ddf21b69372 100644
--- a/include/trace/events/task.h
+++ b/include/trace/events/task.h
@@ -22,6 +22,7 @@ TRACE_EVENT(task_newtask,
 	TP_fast_assign(
 		__entry->pid = task->pid;
 		memcpy(__entry->comm, task->comm, TASK_COMM_LEN);
+		__entry->comm[TASK_COMM_LEN - 1] = '\0';
 		__entry->clone_flags = clone_flags;
 		__entry->oom_score_adj = task->signal->oom_score_adj;
 	),
@@ -45,6 +46,7 @@ TRACE_EVENT(task_rename,
 
 	TP_fast_assign(
 		memcpy(entry->oldcomm, task->comm, TASK_COMM_LEN);
+		entry->oldcomm[TASK_COMM_LEN - 1] = '\0';
 		strscpy(entry->newcomm, comm, TASK_COMM_LEN);
 		__entry->oom_score_adj = task->signal->oom_score_adj;
 	),
-- 
2.38.1