Messages in this thread Patch in this message | | | From | Luis Henriques <> | Subject | [PATCH 3.5 68/96] mm: ensure get_unmapped_area() returns higher address than mmap_min_addr | Date | Mon, 13 Jan 2014 14:24:31 +0000 |
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3.5.7.29 -stable review patch. If anyone has any objections, please let me know.
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From: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
commit 2afc745f3e3079ab16c826be4860da2529054dd2 upstream.
This patch fixes the problem that get_unmapped_area() can return illegal address and result in failing mmap(2) etc.
In case that the address higher than PAGE_SIZE is set to /proc/sys/vm/mmap_min_addr, the address lower than mmap_min_addr can be returned by get_unmapped_area(), even if you do not pass any virtual address hint (i.e. the second argument).
This is because the current get_unmapped_area() code does not take into account mmap_min_addr.
This leads to two actual problems as follows:
1. mmap(2) can fail with EPERM on the process without CAP_SYS_RAWIO, although any illegal parameter is not passed.
2. The bottom-up search path after the top-down search might not work in arch_get_unmapped_area_topdown().
Note: The first and third chunk of my patch, which changes "len" check, are for more precise check using mmap_min_addr, and not for solving the above problem.
[How to reproduce]
--- test.c ------------------------------------------------- #include <stdio.h> #include <unistd.h> #include <sys/mman.h> #include <sys/errno.h>
int main(int argc, char *argv[]) { void *ret = NULL, *last_map; size_t pagesize = sysconf(_SC_PAGESIZE);
do { last_map = ret; ret = mmap(0, pagesize, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); // printf("ret=%p\n", ret); } while (ret != MAP_FAILED);
if (errno != ENOMEM) { printf("ERR: unexpected errno: %d (last map=%p)\n", errno, last_map); }
return 0; } ---------------------------------------------------------------
$ gcc -m32 -o test test.c $ sudo sysctl -w vm.mmap_min_addr=65536 vm.mmap_min_addr = 65536 $ ./test (run as non-priviledge user) ERR: unexpected errno: 1 (last map=0x10000)
Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com> Signed-off-by: Kiyoshi Owada <owada.kiyoshi@jp.panasonic.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> [bwh: Backported to 3.2: As we do not have vm_unmapped_area(), make arch_get_unmapped_area_topdown() calculate the lower limit for the new area's end address and then compare addresses with this instead of with len. In the process, fix an off-by-one error which could result in returning 0 if mm->mmap_base == len.] Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com> [akira: Backported to 3.5: Based on Ben's backport for 3.2-stable kernel. ] Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- mm/mmap.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c index 7e24763..529f72c 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1443,7 +1443,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, struct vm_area_struct *vma; unsigned long start_addr; - if (len > TASK_SIZE) + if (len > TASK_SIZE - mmap_min_addr) return -ENOMEM; if (flags & MAP_FIXED) @@ -1452,7 +1452,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, if (addr) { addr = PAGE_ALIGN(addr); vma = find_vma(mm, addr); - if (TASK_SIZE - len >= addr && + if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && (!vma || addr + len <= vma->vm_start)) return addr; } @@ -1515,9 +1515,10 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, struct vm_area_struct *vma; struct mm_struct *mm = current->mm; unsigned long addr = addr0, start_addr; + unsigned long low_limit = max(PAGE_SIZE, mmap_min_addr); /* requested length too big for entire address space */ - if (len > TASK_SIZE) + if (len > TASK_SIZE - mmap_min_addr) return -ENOMEM; if (flags & MAP_FIXED) @@ -1527,7 +1528,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, if (addr) { addr = PAGE_ALIGN(addr); vma = find_vma(mm, addr); - if (TASK_SIZE - len >= addr && + if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && (!vma || addr + len <= vma->vm_start)) return addr; } @@ -1542,7 +1543,7 @@ try_again: /* either no address requested or can't fit in requested address hole */ start_addr = addr = mm->free_area_cache; - if (addr < len) + if (addr < low_limit + len) goto fail; addr -= len; @@ -1563,7 +1564,7 @@ try_again: /* try just below the current vma->vm_start */ addr = vma->vm_start-len; - } while (len < vma->vm_start); + } while (vma->vm_start >= low_limit + len); fail: /* -- 1.8.3.2
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