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authorHugh Dickins <hughd@google.com>2010-07-30 13:58:26 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2010-07-30 21:56:09 -0400
commitde51257aa301652876ab6e8f13ea4eadbe4a3846 (patch)
tree388ee39bed1d7e362438d047b57399a28e2617f8 /mm
parent51c20fcced5badee0e2021c6c89f44aa3cbd72aa (diff)
mm: fix ia64 crash when gcore reads gate area
Debian's ia64 autobuilders have been seeing kernel freeze or reboot when running the gdb testsuite (Debian bug 588574): dannf bisected to 2.6.32 62eede62dafb4a6633eae7ffbeb34c60dba5e7b1 "mm: ZERO_PAGE without PTE_SPECIAL"; and reproduced it with gdb's gcore on a simple target. I'd missed updating the gate_vma handling in __get_user_pages(): that happens to use vm_normal_page() (nowadays failing on the zero page), yet reported success even when it failed to get a page - boom when access_process_vm() tried to copy that to its intermediate buffer. Fix this, resisting cleanups: in particular, leave it for now reporting success when not asked to get any pages - very probably safe to change, but let's not risk it without testing exposure. Why did ia64 crash with 16kB pages, but succeed with 64kB pages? Because setup_gate() pads each 64kB of its gate area with zero pages. Reported-by: Andreas Barth <aba@not.so.argh.org> Bisected-by: dann frazier <dannf@debian.org> Signed-off-by: Hugh Dickins <hughd@google.com> Tested-by: dann frazier <dannf@dannf.org> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memory.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 119b7ccdf39b..bde42c6d3633 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1394,10 +1394,20 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1394 return i ? : -EFAULT; 1394 return i ? : -EFAULT;
1395 } 1395 }
1396 if (pages) { 1396 if (pages) {
1397 struct page *page = vm_normal_page(gate_vma, start, *pte); 1397 struct page *page;
1398
1399 page = vm_normal_page(gate_vma, start, *pte);
1400 if (!page) {
1401 if (!(gup_flags & FOLL_DUMP) &&
1402 is_zero_pfn(pte_pfn(*pte)))
1403 page = pte_page(*pte);
1404 else {
1405 pte_unmap(pte);
1406 return i ? : -EFAULT;
1407 }
1408 }
1398 pages[i] = page; 1409 pages[i] = page;
1399 if (page) 1410 get_page(page);
1400 get_page(page);
1401 } 1411 }
1402 pte_unmap(pte); 1412 pte_unmap(pte);
1403 if (vmas) 1413 if (vmas)