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Message-Id: <20210121140240.83405-1-alex_y_xu@yahoo.ca>
Date: Thu, 21 Jan 2021 09:02:40 -0500
From: "Alex Xu (Hello71)" <alex_y_xu@...oo.ca>
To: musl@...ts.openwall.com
Cc: "Alex Xu (Hello71)" <alex_y_xu@...oo.ca>
Subject: [PATCH] don't set errno in free
busybox echo fails if free sets errno, which madvise does on old
kernels.
---
src/malloc/mallocng/free.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/src/malloc/mallocng/free.c b/src/malloc/mallocng/free.c
index 40745f97..82836815 100644
--- a/src/malloc/mallocng/free.c
+++ b/src/malloc/mallocng/free.c
@@ -119,7 +119,13 @@ void free(void *p)
if (((uintptr_t)(start-1) ^ (uintptr_t)end) >= 2*PGSZ && g->last_idx) {
unsigned char *base = start + (-(uintptr_t)start & (PGSZ-1));
size_t len = (end-base) & -PGSZ;
- if (len) madvise(base, len, MADV_FREE);
+ if (len) {
+ // madvise(..., MADV_FREE) returns -EINVAL on old kernels
+ // POSIX.1-202x requires free() to not modify errno on success
+ int e = errno;
+ madvise(base, len, MADV_FREE);
+ errno = e;
+ }
}
// atomic free without locking if this is neither first or last slot
@@ -139,5 +145,9 @@ void free(void *p)
wrlock();
struct mapinfo mi = nontrivial_free(g, idx);
unlock();
- if (mi.len) munmap(mi.base, mi.len);
+ // POSIX.1-202x requires free() to not modify errno on success
+ // munmap should succeed but no harm checking it again
+ if (mi.len)
+ if (munmap(mi.base, mi.len))
+ a_crash();
}
--
2.30.0
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