Messages in this thread Patch in this message |  | | Date | Wed, 22 Oct 2014 19:26:07 -0700 (PDT) | From | Davide Libenzi <> | Subject | [patch][resend] MAP_HUGETLB munmap fails with size not 2MB aligned |
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[Resending with proper CC list suggested by Andrew]
Calling munmap on a MAP_HUGETLB area, and a size which is not 2MB aligned, causes munmap to fail. Tested on 3.13.x but tracking back to 3.2.x. In do_munmap() we forcibly want a 4KB default page, and we wrongly calculate the end of the map. Since the calculated end is within the end address of the target vma, we try to do a split with an address right in the middle of a huge page, which would fail with EINVAL.
Tentative (untested) patch and test case attached (be sure you have a few huge pages available via /proc/sys/vm/nr_hugepages tinkering).
Signed-Off-By: Davide Libenzi <davidel@xmailserver.org>
- Davide
diff --git a/mm/mmap.c b/mm/mmap.c index 7f85520..6dba257 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2528,10 +2528,6 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len) if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start) return -EINVAL; - len = PAGE_ALIGN(len); - if (len == 0) - return -EINVAL; - /* Find the first overlapping VMA */ vma = find_vma(mm, start); if (!vma) @@ -2539,6 +2535,16 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len) prev = vma->vm_prev; /* we have start < vma->vm_end */ + if (likely(!is_vm_hugetlb_page(vma))) + len = PAGE_ALIGN(len); + else { + unsigned long hpage_size = huge_page_size(hstate_vma(vma)); + + len = ALIGN(len, hpage_size); + } + if (unlikely(len == 0)) + return -EINVAL; + /* if it doesn't overlap, we have nothing.. */ end = start + len; if (vma->vm_start >= end)
[hugebug.c]
#include <sys/mman.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <errno.h>
static void test(int flags, size_t size) { void* addr = mmap(NULL, size, PROT_READ | PROT_WRITE, flags | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if (addr == MAP_FAILED) { perror("mmap"); exit(1); } *(char*) addr = 17; if (munmap(addr, size) != 0) { perror("munmap"); exit(1); } } int main(int ac, const char** av) { static const size_t hugepage_size = 2 * 1024 * 1024; printf("Testing normal pages with 2MB size ...\n"); test(0, hugepage_size); printf("OK\n");
printf("Testing huge pages with 2MB size ...\n"); test(MAP_HUGETLB, hugepage_size); printf("OK\n");
printf("Testing normal pages with 4KB byte size ...\n"); test(0, 4096); printf("OK\n");
printf("Testing huge pages with 4KB byte size ...\n"); test(MAP_HUGETLB, 4096); printf("OK\n");
printf("Testing normal pages with 1 byte size ...\n"); test(0, 1); printf("OK\n");
printf("Testing huge pages with 1 byte size ...\n"); test(MAP_HUGETLB, 1); printf("OK\n");
return 0; }
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