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Subject[PATCH] Added PR_SET_PROCTITLE_AREA option for prctl()
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Date
PR_SET_PROCTITLE_AREA updates mm_struct->arg_start and arg_end to the
given pointers, which makes it possible for user space to implement
setproctitle(3) cleanly.


Signed-off-by: Timo Sirainen <tss@iki.fi>
---
fs/proc/base.c | 9 ++++++---
include/linux/prctl.h | 2 ++
kernel/sys.c | 10 ++++++++++
3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 837469a..43ef276 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -267,9 +267,12 @@ static int proc_pid_cmdline(struct task_struct *task, char * buffer)

res = access_process_vm(task, mm->arg_start, buffer, len, 0);

- // If the nul at the end of args has been overwritten, then
- // assume application is using setproctitle(3).
- if (res > 0 && buffer[res-1] != '\0' && len < PAGE_SIZE) {
+ if (mm->arg_end != mm->env_start) {
+ // PR_SET_PROCTITLE_AREA used
+ res = strnlen(buffer, res);
+ } else if (res > 0 && buffer[res-1] != '\0' && len < PAGE_SIZE) {
+ // If the nul at the end of args has been overwritten, then
+ // assume application is using old style setproctitle(3).
len = strnlen(buffer, res);
if (len < res) {
res = len;
diff --git a/include/linux/prctl.h b/include/linux/prctl.h
index 9311505..c79ccc8 100644
--- a/include/linux/prctl.h
+++ b/include/linux/prctl.h
@@ -90,4 +90,6 @@

#define PR_MCE_KILL 33

+#define PR_SET_PROCTITLE_AREA 34 /* Set process title memory area */
+
#endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index 255475d..c216ae6 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1564,6 +1564,16 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
error = 0;
break;

+ case PR_SET_PROCTITLE_AREA: {
+ struct mm_struct *mm = current->mm;
+
+ if (arg2 >= arg3)
+ return -EINVAL;
+
+ mm->arg_start = arg2;
+ mm->arg_end = arg3;
+ return 0;
+ }
default:
error = -EINVAL;
break;
--
1.6.3.3



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