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=== Description (from pull-request) ===
`dirname()` behaves differently on `glibc` vs POSIX implementations (e.g. `musl`).
Under `glibc`, the use of `dirname()` terminates at `/` as required, but the same code on `musl` ends at, for example, `/lxc.payload.dear-raccoon`, resulting in an infinite loop when trying to read `/proc/meminfo` in a container.
A simple replacement for `dirname()` solves this on non-`glibc` platforms like Alpine. :smile:
From db36731bf3598d0f6fe5f493b1df59ed6edd16ce Mon Sep 17 00:00:00 2001
From: Jack O'Sullivan <jackos1...@gmail.com>
Date: Thu, 3 Sep 2020 22:39:05 +0100
Subject: [PATCH] Fix `get_min_memlimit()` on non-glibc
Signed-off-by: Jack O'Sullivan <j...@ckos.ie>
---
src/proc_fuse.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/src/proc_fuse.c b/src/proc_fuse.c
index a99162c..7e957d0 100644
--- a/src/proc_fuse.c
+++ b/src/proc_fuse.c
@@ -213,6 +213,25 @@ static uint64_t get_memlimit(const char *cgroup, bool swap)
return memlimit;
}
+/*
+ * dirname() behaves differently on musl than glibc, so implement the bits we
+ * need (the path in this case is always absolute and never ends in a `/`)
+ */
+static char *cgroup_parent(char *cgroup)
+{
+ if (strcmp(cgroup, "/") == 0) {
+ return cgroup;
+ }
+
+ char *last_slash = strrchr(cgroup, '/');
+ if (last_slash == cgroup) {
+ last_slash++;
+ }
+ *last_slash = '\0';
+
+ return cgroup;
+}
+
static uint64_t get_min_memlimit(const char *cgroup, bool swap)
{
__do_free char *copy = NULL;
@@ -227,7 +246,7 @@ static uint64_t get_min_memlimit(const char *cgroup, bool
swap)
while (strcmp(copy, "/") != 0) {
char *it = copy;
- it = dirname(it);
+ it = cgroup_parent(it);
memlimit = get_memlimit(it, swap);
if (memlimit > 0 && memlimit < retlimit)
retlimit = memlimit;
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