From da438ee1fc516c41ba1790cef7be551a9e244397 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 6 Sep 2017 22:09:28 -0400 Subject: work around incorrect EPERM from mmap syscall under some conditions, the mmap syscall wrongly fails with EPERM instead of ENOMEM when memory is exhausted; this is probably the result of the kernel trying to fit the allocation somewhere that crosses into the kernel range or below mmap_min_addr. in any case it's a conformance bug, so work around it. for now, only handle the case of anonymous mappings with no requested address; in other cases EPERM may be a legitimate error. this indirectly fixes the possibility of malloc failing with the wrong errno value. --- src/mman/mmap.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'src/mman/mmap.c') diff --git a/src/mman/mmap.c b/src/mman/mmap.c index 19caadbd..15924033 100644 --- a/src/mman/mmap.c +++ b/src/mman/mmap.c @@ -14,6 +14,7 @@ weak_alias(dummy, __vm_wait); void *__mmap(void *start, size_t len, int prot, int flags, int fd, off_t off) { + long ret; if (off & OFF_MASK) { errno = EINVAL; return MAP_FAILED; @@ -26,10 +27,14 @@ void *__mmap(void *start, size_t len, int prot, int flags, int fd, off_t off) __vm_wait(); } #ifdef SYS_mmap2 - return (void *)syscall(SYS_mmap2, start, len, prot, flags, fd, off/UNIT); + ret = __syscall(SYS_mmap2, start, len, prot, flags, fd, off/UNIT); #else - return (void *)syscall(SYS_mmap, start, len, prot, flags, fd, off); + ret = __syscall(SYS_mmap, start, len, prot, flags, fd, off); #endif + /* Fixup incorrect EPERM from kernel. */ + if (ret == -EPERM && !start && (flags&MAP_ANON) && !(flags&MAP_FIXED)) + ret = -ENOMEM; + return (void *)__syscall_ret(ret); } weak_alias(__mmap, mmap); -- cgit v1.2.1