testing/libmilter: set default pthread stack size to 8 MB

This patch tries to fix various crashes for applications depending on
libmilter by setting the stack size for pthreads to 8 MB. The default
stack size for musl libc is set to 80 KB whereas glibc has it set
to 8 MB. This causes problems when a large amount of memory is
allocated on the stack.

For example, opendkim allocates blocks of 64 KB multiple times, which
causes libmilter (and therefore opendkim) to crash.
Maybe a stack size of 1 MB or 2 MB would be sufficient, but as opendkim
depends on the default glibc behavior, 8 MB should be safe.

I know this patch is kind of ugly, a better solution may be to file
a request for opendkim to allocate large blocks of memory on the heap.
But as libmilter/opendkim are fairly unusable at the moment, I suggest
to apply this patch as long as these packages are in testing.

Fixes https://bugs.alpinelinux.org/issues/6360

1 files changed, 44 insertions, 0 deletions

diff --git a/testing/libmilter/default-pthread-stacksize.patch b/testing/libmilter/default-pthread-stacksize.patch
new file mode 100644
index 0000000000..4e3524c230
--- /dev/null
+++ b/testing/libmilter/default-pthread-stacksize.patch
@@ -0,0 +1,44 @@
+Set default pthread stack size to 8 MB
+
+This patch tries to fix various crashes for applications depending on
+libmilter by setting the stack size for pthreads to 8 MB. The default
+stack size for musl libc is set to 80 KB whereas glibc has it set
+to 8 MB. This causes problems when a large amount of memory is
+allocated on the stack.
+
+For example, opendkim allocates blocks of 64 KB multiple times, which
+causes libmilter (and therefore opendkim) to crash.
+Maybe a stack size of 1 MB or 2 MB would be sufficient, but as opendkim
+depends on the default glibc behavior, 8 MB should be safe.
+
+Fixes https://bugs.alpinelinux.org/issues/6360
+
+--- a/libmilter/libmilter.h
++++ b/libmilter/libmilter.h
+@@ -127,10 +127,10 @@
+ # define MI_SOCK_READ(s, b, l)	read(s, b, l)
+ # define MI_SOCK_READ_FAIL(x)	((x) < 0)
+ # define MI_SOCK_WRITE(s, b, l)	write(s, b, l)
+-
+-# define thread_create(ptid,wr,arg) pthread_create(ptid, NULL, wr, arg)
+ # define sthread_get_id()	pthread_self()
+
++extern int thread_create(pthread_t *ptid, void *(*wr) (void *), void *arg);
++
+ typedef pthread_mutex_t smutex_t;
+ # define smutex_init(mp)	(pthread_mutex_init(mp, NULL) == 0)
+ # define smutex_destroy(mp)	(pthread_mutex_destroy(mp) == 0)
+--- a/libmilter/main.c
++++ b/libmilter/main.c
+@@ -16,6 +16,12 @@
+ #include <fcntl.h>
+ #include <sys/stat.h>
+
++int thread_create(pthread_t *ptid, void *(*wr) (void *), void *arg) {
++	pthread_attr_t attr;
++	pthread_attr_init(&attr);
++	pthread_attr_setstacksize(&attr,8*1024*1024);
++	return pthread_create(ptid, &attr, wr, arg);
++}
+
+ static smfiDesc_ptr smfi = NULL;