On 02/27/2014 02:53 PM, Kirill A. Shutemov wrote: > The patch introduces new vm_ops callback ->map_pages() and uses it for > mapping easy accessible pages around fault address. > > On read page fault, if filesystem provides ->map_pages(), we try to map > up to FAULT_AROUND_PAGES pages around page fault address in hope to > reduce number of minor page faults. > > We call ->map_pages first and use ->fault() as fallback if page by the > offset is not ready to be mapped (cold page cache or something). > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > --- Hi all, This patch triggers use-after-free when fuzzing using trinity and the KASAN patchset. KASAN's report is: [ 663.269187] AddressSanitizer: use after free in do_read_fault.isra.40+0x3c2/0x510 at addr ffff88048a733110 [ 663.275260] page:ffffea001229ccc0 count:0 mapcount:0 mapping: (null) index:0x0 [ 663.277061] page flags: 0xafffff80008000(tail) [ 663.278759] page dumped because: kasan error [ 663.280645] CPU: 6 PID: 9262 Comm: trinity-c104 Not tainted 3.16.0-rc6-next-20140723-sasha-00047-g289342b-dirty #929 [ 663.282898] 00000000000000fb 0000000000000000 ffffea001229ccc0 ffff88038ac0fb78 [ 663.288759] ffffffffa5e40903 ffff88038ac0fc48 ffff88038ac0fc38 ffffffffa142acfc [ 663.291496] 0000000000000001 ffff880509ff5aa8 ffff88038ac10038 ffff88038ac0fbb0 [ 663.294379] Call Trace: [ 663.294806] dump_stack (lib/dump_stack.c:52) [ 663.300665] kasan_report_error (mm/kasan/report.c:98 mm/kasan/report.c:166) [ 663.301659] ? debug_smp_processor_id (lib/smp_processor_id.c:57) [ 663.304645] ? preempt_count_sub (kernel/sched/core.c:2606) [ 663.305800] ? put_lock_stats.isra.13 (./arch/x86/include/asm/preempt.h:98 kernel/locking/lockdep.c:254) [ 663.306839] ? do_read_fault.isra.40 (mm/memory.c:2784 mm/memory.c:2849 mm/memory.c:2898) [ 663.307515] __asan_load8 (mm/kasan/kasan.c:364) [ 663.308038] ? do_read_fault.isra.40 (mm/memory.c:2864 mm/memory.c:2898) [ 663.309158] do_read_fault.isra.40 (mm/memory.c:2864 mm/memory.c:2898) [ 663.310311] ? _raw_spin_unlock (./arch/x86/include/asm/preempt.h:98 include/linux/spinlock_api_smp.h:152 kernel/locking/spinlock.c:183) [ 663.311282] ? __pte_alloc (mm/memory.c:598) [ 663.312331] handle_mm_fault (mm/memory.c:3092 mm/memory.c:3225 mm/memory.c:3345 mm/memory.c:3374) [ 663.313895] ? pud_huge (./arch/x86/include/asm/paravirt.h:611 arch/x86/mm/hugetlbpage.c:76) [ 663.314793] __get_user_pages (mm/gup.c:286 mm/gup.c:478) [ 663.315775] __mlock_vma_pages_range (mm/mlock.c:262) [ 663.316879] __mm_populate (mm/mlock.c:710) [ 663.317813] SyS_remap_file_pages (mm/mmap.c:2653 mm/mmap.c:2593) [ 663.318848] tracesys (arch/x86/kernel/entry_64.S:541) [ 663.319683] Read of size 8 by thread T9262: [ 663.320580] Memory state around the buggy address: [ 663.321392] ffff88048a732e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 663.322573] ffff88048a732f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 663.323802] ffff88048a732f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 663.325080] ffff88048a733000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 663.326327] ffff88048a733080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 663.327572] >ffff88048a733100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 663.328840] ^ [ 663.329487] ffff88048a733180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 663.330762] ffff88048a733200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 663.331994] ffff88048a733280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 663.333262] ffff88048a733300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 663.334488] ffff88048a733380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb This also proceeds with the traditional: [ 663.474532] BUG: unable to handle kernel paging request at ffff88048a635de8 [ 663.474548] IP: do_read_fault.isra.40 (mm/memory.c:2864 mm/memory.c:2898) But the rest of it got scrambled between the KASAN prints and the other BUG info + trace (who broke printk?!). Thanks, Sasha -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>