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util-lib: do not truncate kernel comm names 

It turns out that the kernel allows comm names higher than our expected limit
of 16.
$ wc -c /proc/*/comm|sort -g|tail -n3
35 /proc/1292317/comm
35 /proc/1293610/comm
36 /proc/1287112/comm
$ cat /proc/1287112/comm
kworker/u9:3-kcryptd/253:0
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2019-05-15 11:55:59 +02:00
parent bc28751ed2
commit 0e85cbcfc3
2 changed files with 16 additions and 9 deletions
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11
src/basic/process-util.c
View File

@ -46,6 +46,11 @@
#include "user-util.h"
#include "utf8.h"
/* The kernel limits userspace processes to TASK_COMM_LEN (16 bytes), but allows higher values for its own
* workers, e.g. "kworker/u9:3-kcryptd/253:0". Let's pick a fixed smallish limit that will work for the kernel.
*/
#define COMM_MAX_LEN 128
static int get_process_state(pid_t pid) {
const char *p;
char state;
@ -82,7 +87,7 @@ int get_process_comm(pid_t pid, char **ret) {
assert(ret);
assert(pid >= 0);
escaped = new(char, TASK_COMM_LEN);
escaped = new(char, COMM_MAX_LEN);
if (!escaped)
return -ENOMEM;
@ -95,7 +100,7 @@ int get_process_comm(pid_t pid, char **ret) {
return r;
/* Escape unprintable characters, just in case, but don't grow the string beyond the underlying size */
cellescape(escaped, TASK_COMM_LEN, comm);
cellescape(escaped, COMM_MAX_LEN, comm);
*ret = TAKE_PTR(escaped);
return 0;
@ -209,7 +214,7 @@ int rename_process(const char name[]) {
* can use PR_SET_NAME, which sets the thread name for the calling thread. */
if (prctl(PR_SET_NAME, name) < 0)
log_debug_errno(errno, "PR_SET_NAME failed: %m");
if (l >= TASK_COMM_LEN) /* Linux process names can be 15 chars at max */
if (l >= TASK_COMM_LEN) /* Linux userspace process names can be 15 chars at max */
truncated = true;
/* Second step, change glibc's ID of the process name. */

14
src/test/test-process-util.c
View File

@ -107,12 +107,12 @@ static void test_get_process_comm_escape(void) {
test_get_process_comm_escape_one("foo", "foo");
test_get_process_comm_escape_one("012345678901234", "012345678901234");
test_get_process_comm_escape_one("0123456789012345", "012345678901234");
test_get_process_comm_escape_one("äöüß", "\\303\\244\\303…");
test_get_process_comm_escape_one("xäöüß", "x\\303\\244…");
test_get_process_comm_escape_one("xxäöüß", "xx\\303\\244…");
test_get_process_comm_escape_one("xxxäöüß", "xxx\\303\\244…");
test_get_process_comm_escape_one("xxxxäöüß", "xxxx\\303\\244…");
test_get_process_comm_escape_one("xxxxxäöüß", "xxxxx\\303…");
test_get_process_comm_escape_one("äöüß", "\\303\\244\\303\\266\\303\\274\\303\\237");
test_get_process_comm_escape_one("xäöüß", "x\\303\\244\\303\\266\\303\\274\\303\\237");
test_get_process_comm_escape_one("xxäöüß", "xx\\303\\244\\303\\266\\303\\274\\303\\237");
test_get_process_comm_escape_one("xxxäöüß", "xxx\\303\\244\\303\\266\\303\\274\\303\\237");
test_get_process_comm_escape_one("xxxxäöüß", "xxxx\\303\\244\\303\\266\\303\\274\\303\\237");
test_get_process_comm_escape_one("xxxxxäöüß", "xxxxx\\303\\244\\303\\266\\303\\274\\303\\237");
assert_se(prctl(PR_SET_NAME, saved) >= 0);
}
@ -407,6 +407,8 @@ static void test_rename_process_now(const char *p, int ret) {
assert_se(get_process_comm(0, &comm) >= 0);
log_info("comm = <%s>", comm);
assert_se(strneq(comm, p, TASK_COMM_LEN-1));
/* We expect comm to be at most 16 bytes (TASK_COMM_LEN). The kernel may raise this limit in the
* future. We'd only check the initial part, at least until we recompile, but this will still pass. */
r = get_process_cmdline(0, SIZE_MAX, false, &cmdline);
assert_se(r >= 0);