This is an automated email from the ASF dual-hosted git repository.
acassis pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/nuttx.git
The following commit(s) were added to refs/heads/master by this push:
new ef37425f71c sched: fix 1-byte overflow in prctl(PR_GET_NAME)
ef37425f71c is described below
commit ef37425f71cdaf6c78ef966e05e77939c1f0b78b
Author: Junbo Zheng <[email protected]>
AuthorDate: Sun Sep 13 17:38:40 2026 +0800
sched: fix 1-byte overflow in prctl(PR_GET_NAME)
strlcpy() was given sizeof(tcb->name), i.e. CONFIG_TASK_NAME_SIZE + 1,
but the documented caller contract is a buffer of CONFIG_TASK_NAME_SIZE
bytes (include/sys/prctl.h). When a task name is exactly
CONFIG_TASK_NAME_SIZE chars (the normal result of nxtask_setup_name()
truncation), the terminating NUL lands one byte past the caller buffer.
Pass CONFIG_TASK_NAME_SIZE to strlcpy() so the copy is truncated
in-bounds, and drop the stale forced-NUL line left over from the strncpy
era (it ran after the overflow had already happened).
Before:
```
guard byte placed right after a CONFIG_TASK_NAME_SIZE caller buffer
reads 0x00 (expected 0xAA) after the call: strlcpy writes its
terminating NUL one byte past the buffer when the task name is exactly
CONFIG_TASK_NAME_SIZE chars.
```
After:
```
strlcpy(name, tcb->name, CONFIG_TASK_NAME_SIZE) writes at most
CONFIG_TASK_NAME_SIZE bytes; the caller buffer stays intact.
```
Testing:
Simulated (sim:nsh, CONFIG_TASK_NAME_SIZE=31).
Build and run:
```
cmake -B build -DBOARD_CONFIG=sim:nsh -GNinja
cmake --build build -j$(nproc)
echo hello | ./build/nuttx
```
then run "hello" at the NSH prompt.
The test was carried by apps/examples/hello/hello_main.c (scratch only,
not part of this commit); its diff:
```
--- a/examples/hello/hello_main.c
+++ b/examples/hello/hello_main.c
@@ -24,6 +24,8 @@
#include <nuttx/config.h>
#include <stdio.h>
+#include <string.h>
+#include <sys/prctl.h>
/****************************************************************************
* Public Functions
@@ -35,6 +37,55 @@
int main(int argc, FAR char *argv[])
{
+ /* Longest-legal task name: exactly CONFIG_TASK_NAME_SIZE chars, the
+ * normal result of nxtask_setup_name() truncation.
+ */
+
+ static const char longname[] =
+ "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+
+ /* Caller buffer per the documented prctl(PR_GET_NAME) contract, with a
+ * guard byte immediately after it to detect the 1-byte overflow.
+ */
+
+ struct
+ {
+ char buf[CONFIG_TASK_NAME_SIZE];
+ volatile unsigned char guard;
+ } s;
+
+ _Static_assert(sizeof(longname) - 1 > CONFIG_TASK_NAME_SIZE,
+ "test name must exceed CONFIG_TASK_NAME_SIZE");
+
printf("Hello, World!!\n");
+ printf("prctl test: CONFIG_TASK_NAME_SIZE=%d\n", CONFIG_TASK_NAME_SIZE);
+
+ s.guard = 0xaa;
+ s.buf[0] = '\0';
+
+ if (prctl(PR_SET_NAME, (unsigned long)longname) != 0)
+ {
+ printf("prctl test: PR_SET_NAME failed\n");
+ return 1;
+ }
+
+ if (prctl(PR_GET_NAME, (unsigned long)s.buf) != 0)
+ {
+ printf("prctl test: PR_GET_NAME failed\n");
+ return 1;
+ }
+
+ printf("prctl test: guard=0x%02x (expected 0xaa), name len=%zu, "
+ "last char=0x%02x\n",
s.guard, strlen(s.buf), (unsigned char)s.buf[strlen(s.buf)]);
+
+ if (s.guard != 0xaa)
+ {
+ printf("prctl test: FAIL - terminating NUL written 1 byte past "
+ "the caller buffer\n");
+ return 1;
+ }
+
+ printf("prctl test: PASS - caller buffer intact\n");
return 0;
}
```
Before the fix:
```
prctl test: guard=0x00 (expected 0xaa), name len=30, last char=0x00
prctl test: FAIL - terminating NUL written 1 byte past the caller buffer
```
After the fix:
```
prctl test: guard=0xaa (expected 0xaa), name len=30, last char=0x00
prctl test: PASS - caller buffer intact
```
Assisted-by: Claude Code (GLM-5.3) <[email protected]>
Signed-off-by: Junbo Zheng <[email protected]>
---
sched/task/task_prctl.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/sched/task/task_prctl.c b/sched/task/task_prctl.c
index 8b41979e89d..b065eeae833 100644
--- a/sched/task/task_prctl.c
+++ b/sched/task/task_prctl.c
@@ -137,8 +137,7 @@ int prctl(int option, ...)
* necessary.
*/
- strlcpy(name, tcb->name, sizeof(tcb->name));
- name[CONFIG_TASK_NAME_SIZE - 1] = '\0';
+ strlcpy(name, tcb->name, CONFIG_TASK_NAME_SIZE);
}
}
break;
