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Message-ID: <ee1c6d93-9ef9-5dc8-0b0b-d039e5a2e0dd@davolink.co.kr>
Date: Tue, 28 Jan 2020 14:44:07 +0900
From: Leesoo Ahn <yisooan@...olink.co.kr>
To: musl@...ts.openwall.com
Subject: Memory leak issue in multi-threaded program
Dear musl developers,
Hello!, it seems that musl currently has a memory leak issue in
multi-threaded program. It occurs in the below situation of latest
(v1.1.24) source. Also, not only in 32-bits[1], but also 64-bits[2] as
well.
When a program create and run, at least, two threads or more with
pthread APIs, VSZ of the program by ps command keeps increasing. But
here is a weird thing that it is fine 'IF ONLY ONE' pthread is created
and run.
To confirm the issue in your host machine, please follow the instructions,
0. Clone the musl git and get inside.
1. Build with these options for static build, ./configure
--prefix=$(pwd)/_build_dir --disable-shared
2. Download the test code[3], then build with the command,
./_build_dir/bin/musl-gcc ./test.c
3. Run this script, ./a.out &; while [ 1 ]; do { ps aux | grep [a].out |
grep -v grep; sleep 1; } done
You may figure out that VSZ keeps increasing.
BUT, when I make it to try to allocate memory all the time by kernel
mmap with this diff[4] as workaround, although it creates more pthreads
than 2, the issue never happens.
It would be really thankful if you guys could confirm it and find out
the way to fix the bug.
Thank you in advance and take care.
Best Regards,
Leesoo
----
[1] 32-bits env: https://pastebin.com/xR4PySaM
[2] 64-bits env: https://pastebin.com/stdVQXdE
[3] test code: https://pastebin.com/0s8nmdUv
[4] workaround patch:
diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c
index 9698259..3d39be7 100644
--- a/src/malloc/malloc.c
+++ b/src/malloc/malloc.c
@@ -288,7 +288,11 @@ void *malloc(size_t n)
if (adjust_size(&n) < 0) return 0;
+#if 1
+ if ( 1 ) {
+#else
if (n > MMAP_THRESHOLD) {
+#endif
size_t len = n + OVERHEAD + PAGE_SIZE - 1 & -PAGE_SIZE;
char *base = __mmap(0, len, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
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