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authorHugh Dickins <hughd@google.com>2010-07-30 17:58:26 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2010-07-31 01:56:09 (GMT)
commitde51257aa301652876ab6e8f13ea4eadbe4a3846 (patch)
tree388ee39bed1d7e362438d047b57399a28e2617f8
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>
-rw-r--r--mm/memory.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 119b7cc..bde42c6 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,
return i ? : -EFAULT;
}
if (pages) {
- struct page *page = vm_normal_page(gate_vma, start, *pte);
+ struct page *page;
+
+ page = vm_normal_page(gate_vma, start, *pte);
+ if (!page) {
+ if (!(gup_flags & FOLL_DUMP) &&
+ is_zero_pfn(pte_pfn(*pte)))
+ page = pte_page(*pte);
+ else {
+ pte_unmap(pte);
+ return i ? : -EFAULT;
+ }
+ }
pages[i] = page;
- if (page)
- get_page(page);
+ get_page(page);
}
pte_unmap(pte);
if (vmas)

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