[PATCH v6 2/3] treewide: Switch memcpy() users of 'task->comm' to a more safer implementation

Bhupesh
2025-07-24T12:36:42Z

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@mail.gmail.com/

Signed-off-by: Bhupesh <bhupesh@igalia.com>
---
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 6aa79e2d799c..dfc20fbe389c 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