On exec, single-threading must be enforced before arguments space is

allocated from exec_map.  If many threads try to perform execve(2) in
parallel, the exec map is exhausted and some threads sleep
uninterruptible waiting for the map space.  Then, the thread which won
the race for the space allocation, cannot single-thread the process,
causing deadlock.

Reported and tested by:	pho (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks

1 files changed, 9 insertions, 1 deletions

diff --git a/sys/amd64/linux32/linux32_machdep.c b/sys/amd64/linux32/linux32_machdep.c
index 2b955d0..155e90b 100644
--- a/sys/amd64/linux32/linux32_machdep.c
+++ b/sys/amd64/linux32/linux32_machdep.c
@@ -137,6 +137,7 @@ int
 linux_execve(struct thread *td, struct linux_execve_args *args)
 {
 	struct image_args eargs;
+	struct vmspace *oldvmspace;
 	char *path;
 	int error;
 
@@ -147,12 +148,17 @@ linux_execve(struct thread *td, struct linux_execve_args *args)
 		printf(ARGS(execve, "%s"), path);
 #endif
 
+	error = pre_execve(td, &oldvmspace);
+	if (error != 0) {
+		free(path, M_TEMP);
+		return (error);
+	}
 	error = freebsd32_exec_copyin_args(&eargs, path, UIO_SYSSPACE,
 	    args->argp, args->envp);
 	free(path, M_TEMP);
 	if (error == 0)
 		error = kern_execve(td, &eargs, NULL);
-	if (error == 0)
+	if (error == 0) {
 		/* Linux process can execute FreeBSD one, do not attempt
 		 * to create emuldata for such process using
 		 * linux_proc_init, this leads to a panic on KASSERT
@@ -160,6 +166,8 @@ linux_execve(struct thread *td, struct linux_execve_args *args)
 		 */
 		if (SV_PROC_ABI(td->td_proc) == SV_ABI_LINUX)
 			error = linux_proc_init(td, 0, 0);
+	}
+	post_execve(td, error, oldvmspace);
 	return (error);
 }