diff options
| author | Hugh Dickins <hughd@google.com> | 2010-07-30 10:58:26 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-07-30 18:56:09 -0700 |
| commit | de51257aa301652876ab6e8f13ea4eadbe4a3846 (patch) | |
| tree | 388ee39bed1d7e362438d047b57399a28e2617f8 | |
| parent | 51c20fcced5badee0e2021c6c89f44aa3cbd72aa (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.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/mm/memory.c b/mm/memory.c index 119b7ccdf39..bde42c6d363 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) |