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Fix SELinux mprotect execheap error due to mem adjacent to heap #12942

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Fix SELinux mprotect execheap error due to mem adjacent to heap #12942

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16 changes: 15 additions & 1 deletion ext/opcache/shared_alloc_mmap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,18 @@ static void *find_prefered_mmap_base(size_t requested_size)
}

while (fgets(buffer, MAXPATHLEN, f) && sscanf(buffer, "%lx-%lx", &start, &end) == 2) {
/* Don't place the segment directly before or after the heap segment. Due to an selinux bug,
* a segment directly preceding or following the heap is interpreted as heap memory, which
* will result in an execheap violation for the JIT.
* See https://bugzilla.kernel.org/show_bug.cgi?id=218258. */
bool heap_segment = strstr(buffer, "[heap]") != NULL;
if (heap_segment) {
uintptr_t start_base = start & ~(huge_page_size - 1);
if (last_free_addr + requested_size >= start_base) {
last_free_addr = ZEND_MM_ALIGNED_SIZE_EX(end + huge_page_size, huge_page_size);
continue;
}
}
if ((uintptr_t)execute_ex >= start) {
/* the current segment lays before PHP .text segment or PHP .text segment itself */
if (last_free_addr + requested_size <= start) {
Expand Down Expand Up @@ -90,7 +102,9 @@ static void *find_prefered_mmap_base(size_t requested_size)
}
}
last_free_addr = ZEND_MM_ALIGNED_SIZE_EX(end, huge_page_size);

if (heap_segment) {
last_free_addr += huge_page_size;
}
}
fclose(f);
#elif defined(__FreeBSD__)
Expand Down