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authorRich Felker <dalias@aerifal.cx>2011-03-09 20:07:24 -0500
committerRich Felker <dalias@aerifal.cx>2011-03-09 20:07:24 -0500
commit0bed7e0acfd34e3fb63ca0e4d99b7592571355a9 (patch)
tree3fe63a6e5ab2227639ed4154a8449c21819afeac
parent370f78f2c80c64b7b0780a01e672494a26b5678e (diff)
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fix race condition in raise - just mask signals
a signal handler could fork after the pid/tid were read, causing the
wrong process to be signalled. i'm not sure if this is supposed to
have UB or not, but raise is async-signal-safe, so it probably is
allowed. the current solution is slightly expensive so this
implementation is likely to be changed in the future.
-rw-r--r--src/signal/raise.c18
1 files changed, 9 insertions, 9 deletions
diff --git a/src/signal/raise.c b/src/signal/raise.c
index f437d23f..cc2b19b7 100644
--- a/src/signal/raise.c
+++ b/src/signal/raise.c
@@ -2,17 +2,17 @@
 #include <errno.h>
 #include "syscall.h"
 
+int __sigprocmask(int, const sigset_t *, sigset_t *);
+
 int raise(int sig)
 {
 	int pid, tid, ret;
-	/* Getting the pid/tid pair is not atomic, and could give wrong
-	 * result if a fork occurs in a signal handler between the two
-	 * syscalls. Use the tgkill syscall's ESRCH semantics to detect
-	 * this condition and retry. */
-	do {
-		tid = syscall0(__NR_gettid);
-		pid = syscall0(__NR_getpid);
-		ret = syscall3(__NR_tgkill, pid, tid, sig);
-	} while (ret<0 && errno == ESRCH);
+	sigset_t set;
+	sigfillset(&set);
+	__sigprocmask(SIG_BLOCK, &set, &set);
+	tid = syscall0(__NR_gettid);
+	pid = syscall0(__NR_getpid);
+	ret = syscall3(__NR_tgkill, pid, tid, sig);
+	__sigprocmask(SIG_SETMASK, &set, 0);
 	return ret;
 }