exec: kill bprm->tcomm[], simplify the "basename" logic

Starting from commit c4ad8f98bef7 ("execve: use 'struct filename *' for
executable name passing") bprm->filename can not go away after
flush_old_exec(), so we do not need to save the binary name in
bprm->tcomm[] added by 96e02d158678 ("exec: fix use-after-free bug in
setup_new_exec()").

And there was never need for filename_to_taskname-like code, we can
simply do set_task_comm(kbasename(filename).

This patch has to change set_task_comm() and trace_task_rename() to
accept "const char *", but I think this change is also good.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 1 insertions, 2 deletions

diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index b4a745d7d9a9..61f29e5ea840 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -44,7 +44,6 @@ struct linux_binprm {
         unsigned interp_flags;
         unsigned interp_data;
         unsigned long loader, exec;
-        char tcomm[TASK_COMM_LEN];
 };
 
 #define BINPRM_FLAGS_ENFORCE_NONDUMP_BIT 0
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6c70645eb3b6..f8497059f88c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2357,7 +2357,7 @@ extern long do_fork(unsigned long, unsigned long, unsigned long, int __user *, i
 struct task_struct *fork_idle(int);
 extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
 
-extern void set_task_comm(struct task_struct *tsk, char *from);
+extern void set_task_comm(struct task_struct *tsk, const char *from);
 extern char *get_task_comm(char *to, struct task_struct *tsk);
 
 #ifdef CONFIG_SMP