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signal: Simplify and fix kdb_send_sig 

- Rename from kdb_send_sig_info to kdb_send_sig
  As there is no meaningful siginfo sent

- Use SEND_SIG_PRIV instead of generating a siginfo for a kdb
  signal.  The generated siginfo had a bogus rationale and was
  not correct in the face of pid namespaces.  SEND_SIG_PRIV
  is simpler and actually correct.

- As the code grabs siglock just send the signal with siglock
  held instead of dropping siglock and attempting to grab it again.

- Move the sig_valid test into kdb_kill where it can generate
  a good error message.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2017-08-17 15:45:38 -05:00
parent 30a7acd573
commit 0b44bf9a6f
3 changed files with 10 additions and 16 deletions
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10
kernel/debug/kdb/kdb_main.c
View File

@ -2441,7 +2441,6 @@ static int kdb_kill(int argc, const char **argv)
long sig, pid; long sig, pid;
char *endp; char *endp;
struct task_struct *p; struct task_struct *p;
struct siginfo info;
if (argc != 2) if (argc != 2)
return KDB_ARGCOUNT; return KDB_ARGCOUNT;
@ -2449,7 +2448,7 @@ static int kdb_kill(int argc, const char **argv)
sig = simple_strtol(argv[1], &endp, 0); sig = simple_strtol(argv[1], &endp, 0);
if (*endp) if (*endp)
return KDB_BADINT; return KDB_BADINT;
if (sig >= 0) { if ((sig >= 0) || !valid_signal(-sig)) {
kdb_printf("Invalid signal parameter.<-signal>\n"); kdb_printf("Invalid signal parameter.<-signal>\n");
return 0; return 0;
} }
@ -2470,12 +2469,7 @@ static int kdb_kill(int argc, const char **argv)
return 0; return 0;
} }
p = p->group_leader; p = p->group_leader;
info.si_signo = sig; kdb_send_sig(p, sig);
info.si_errno = 0;
info.si_code = SI_USER;
info.si_pid = pid; /* same capabilities as process being signalled */
info.si_uid = 0; /* kdb has root authority */
kdb_send_sig_info(p, &info);
return 0; return 0;
} }

2
kernel/debug/kdb/kdb_private.h
View File

@ -208,7 +208,7 @@ extern unsigned long kdb_task_state(const struct task_struct *p,
extern void kdb_ps_suppressed(void); extern void kdb_ps_suppressed(void);
extern void kdb_ps1(const struct task_struct *p); extern void kdb_ps1(const struct task_struct *p);
extern void kdb_print_nameval(const char *name, unsigned long val); extern void kdb_print_nameval(const char *name, unsigned long val);
extern void kdb_send_sig_info(struct task_struct *p, struct siginfo *info); extern void kdb_send_sig(struct task_struct *p, int sig);
extern void kdb_meminfo_proc_show(void); extern void kdb_meminfo_proc_show(void);
extern char *kdb_getstr(char *, size_t, const char *); extern char *kdb_getstr(char *, size_t, const char *);
extern void kdb_gdb_state_pass(char *buf); extern void kdb_gdb_state_pass(char *buf);

14
kernel/signal.c
View File

@ -3684,26 +3684,25 @@ void __init signals_init(void)
#ifdef CONFIG_KGDB_KDB #ifdef CONFIG_KGDB_KDB
#include <linux/kdb.h> #include <linux/kdb.h>
/* /*
* kdb_send_sig_info - Allows kdb to send signals without exposing * kdb_send_sig - Allows kdb to send signals without exposing
* signal internals. This function checks if the required locks are * signal internals. This function checks if the required locks are
* available before calling the main signal code, to avoid kdb * available before calling the main signal code, to avoid kdb
* deadlocks. * deadlocks.
*/ */
void void kdb_send_sig(struct task_struct *t, int sig)
kdb_send_sig_info(struct task_struct *t, struct siginfo *info)
{ {
static struct task_struct *kdb_prev_t; static struct task_struct *kdb_prev_t;
int sig, new_t; int new_t, ret;
if (!spin_trylock(&t->sighand->siglock)) { if (!spin_trylock(&t->sighand->siglock)) {
kdb_printf("Can't do kill command now.\n" kdb_printf("Can't do kill command now.\n"
"The sigmask lock is held somewhere else in " "The sigmask lock is held somewhere else in "
"kernel, try again later\n"); "kernel, try again later\n");
return; return;
} }
spin_unlock(&t->sighand->siglock);
new_t = kdb_prev_t != t; new_t = kdb_prev_t != t;
kdb_prev_t = t; kdb_prev_t = t;
if (t->state != TASK_RUNNING && new_t) { if (t->state != TASK_RUNNING && new_t) {
spin_unlock(&t->sighand->siglock);
kdb_printf("Process is not RUNNING, sending a signal from " kdb_printf("Process is not RUNNING, sending a signal from "
"kdb risks deadlock\n" "kdb risks deadlock\n"
"on the run queue locks. " "on the run queue locks. "
@ -3712,8 +3711,9 @@ kdb_send_sig_info(struct task_struct *t, struct siginfo *info)
"the deadlock.\n"); "the deadlock.\n");
return; return;
} }
sig = info->si_signo; ret = send_signal(sig, SEND_SIG_PRIV, t, false);
if (send_sig_info(sig, info, t)) spin_unlock(&t->sighand->siglock);
if (ret)
kdb_printf("Fail to deliver Signal %d to process %d.\n", kdb_printf("Fail to deliver Signal %d to process %d.\n",
sig, t->pid); sig, t->pid);
else else