Message-ID: <CAGsJ_4xMdyBxwwh1AQeFM5a_ZMV2=y68M9eEuJf-D6NtYP-8dA@mail.gmail.com>
Date: Tue, 28 May 2024 20:39:55 +1200
From: Barry Song <21cnbao@...il.com>
To: Mark Rutland <mark.rutland@....com>
Cc: Will Deacon <will@...nel.org>, akpm@...ux-foundation.org, linux-mm@...ck.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Barry Song <v-songbaohua@...o.com>, Lance Yang <ioworker0@...il.com>, 
	Ryan Roberts <ryan.roberts@....com>, David Hildenbrand <david@...hat.com>, Jeff Xie <xiehuan09@...il.com>, 
	Kefeng Wang <wangkefeng.wang@...wei.com>, Michal Hocko <mhocko@...e.com>, 
	Minchan Kim <minchan@...nel.org>, Muchun Song <songmuchun@...edance.com>, 
	Peter Xu <peterx@...hat.com>, Yang Shi <shy828301@...il.com>, 
	Yin Fengwei <fengwei.yin@...el.com>, "Zach O'Keefe" <zokeefe@...gle.com>, 
	Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH] mm: arm64: Fix the out-of-bounds issue in contpte_clear_young_dirty_ptes

On Tue, May 28, 2024 at 8:26 PM Mark Rutland <mark.rutland@....com> wrote:
>
> On Fri, May 24, 2024 at 12:54:44PM +1200, Barry Song wrote:
> > From: Barry Song <v-songbaohua@...o.com>
> >
> > We are passing a huge nr to __clear_young_dirty_ptes() right
> > now. While we should pass the number of pages, we are actually
> > passing CONT_PTE_SIZE. This is causing lots of crashes of
> > MADV_FREE, panic oops could vary everytime.
> >
> > Fixes: 89e86854fb0a ("mm/arm64: override clear_young_dirty_ptes() batch helper")
>
> I was seeing ths same thing on v6.10-rc1 (syzkaller splat and reproducer
> included at the end of the mail). The patch makes sense to me, and fixed the
> splat in testing, so:
>
> Reviewed-by: Mark Rutland <mark.rutland@....com>
> Tested-by: Mark Rutland <mark.rutland@....com>

Thanks!

>
> Since this only affects arm64 and is already in mainline, I assume the fix
> should go via the arm64 tree even though the broken commit went via mm.


Either mm or arm64 is fine with me, but I noticed that Andrew has already
included it in mm-hotfixes-unstable. If it works, we may want to stick with
that. :-)


>
> Mark.
>
> > Cc: Lance Yang <ioworker0@...il.com>
> > Cc: Barry Song <21cnbao@...il.com>
> > Cc: Ryan Roberts <ryan.roberts@....com>
> > Cc: David Hildenbrand <david@...hat.com>
> > Cc: Jeff Xie <xiehuan09@...il.com>
> > Cc: Kefeng Wang <wangkefeng.wang@...wei.com>
> > Cc: Michal Hocko <mhocko@...e.com>
> > Cc: Minchan Kim <minchan@...nel.org>
> > Cc: Muchun Song <songmuchun@...edance.com>
> > Cc: Peter Xu <peterx@...hat.com>
> > Cc: Yang Shi <shy828301@...il.com>
> > Cc: Yin Fengwei <fengwei.yin@...el.com>
> > Cc: Zach O'Keefe <zokeefe@...gle.com>
> > Cc: Catalin Marinas <catalin.marinas@....com>
> > Cc: Will Deacon <will@...nel.org>
> > Signed-off-by: Barry Song <v-songbaohua@...o.com>
> > ---
> >  arch/arm64/mm/contpte.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
> > index 9f9486de0004..a3edced29ac1 100644
> > --- a/arch/arm64/mm/contpte.c
> > +++ b/arch/arm64/mm/contpte.c
> > @@ -376,7 +376,7 @@ void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
> >        * clearing access/dirty for the whole block.
> >        */
> >       unsigned long start = addr;
> > -     unsigned long end = start + nr;
> > +     unsigned long end = start + nr * PAGE_SIZE;
> >
> >       if (pte_cont(__ptep_get(ptep + nr - 1)))
> >               end = ALIGN(end, CONT_PTE_SIZE);
> > @@ -386,7 +386,7 @@ void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
> >               ptep = contpte_align_down(ptep);
> >       }
> >
> > -     __clear_young_dirty_ptes(vma, start, ptep, end - start, flags);
> > +     __clear_young_dirty_ptes(vma, start, ptep, (end - start) / PAGE_SIZE, flags);
> >  }
> >  EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes);
> >
> > --
> > 2.34.1
>
> ---->8----
> Syzkaller hit 'KASAN: use-after-free Read in contpte_clear_young_dirty_ptes' bug.
>
> ==================================================================
> BUG: KASAN: use-after-free in __ptep_get arch/arm64/include/asm/pgtable.h:315 [inline]
> BUG: KASAN: use-after-free in __clear_young_dirty_ptes arch/arm64/include/asm/pgtable.h:1309 [inline]
> BUG: KASAN: use-after-free in contpte_clear_young_dirty_ptes+0x264/0x288 arch/arm64/mm/contpte.c:389
> Read of size 8 at addr ffff000018c0d000 by task syz-executor392/193
>
> CPU: 0 PID: 193 Comm: syz-executor392 Not tainted 6.10.0-rc1-00001-g30b7f99b25b6 #1
> Hardware name: linux,dummy-virt (DT)
> Call trace:
>  dump_backtrace+0x12c/0x1f8 arch/arm64/kernel/stacktrace.c:317
>  show_stack+0x34/0x50 arch/arm64/kernel/stacktrace.c:324
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0x184/0x360 lib/dump_stack.c:114
>  print_address_description mm/kasan/report.c:377 [inline]
>  print_report+0xf4/0x5b0 mm/kasan/report.c:488
>  kasan_report+0xc0/0x100 mm/kasan/report.c:601
>  __asan_report_load8_noabort+0x20/0x30 mm/kasan/report_generic.c:381
>  __ptep_get arch/arm64/include/asm/pgtable.h:315 [inline]
>  __clear_young_dirty_ptes arch/arm64/include/asm/pgtable.h:1309 [inline]
>  contpte_clear_young_dirty_ptes+0x264/0x288 arch/arm64/mm/contpte.c:389
>  clear_young_dirty_ptes arch/arm64/include/asm/pgtable.h:1715 [inline]
>  madvise_free_pte_range+0xa5c/0x16d8 mm/madvise.c:767
>  walk_pmd_range mm/pagewalk.c:143 [inline]
>  walk_pud_range mm/pagewalk.c:221 [inline]
>  walk_p4d_range mm/pagewalk.c:256 [inline]
>  walk_pgd_range+0xca4/0x1900 mm/pagewalk.c:293
>  __walk_page_range+0x4bc/0x5b8 mm/pagewalk.c:395
>  walk_page_range+0x4a4/0x840 mm/pagewalk.c:521
>  madvise_free_single_vma+0x3a0/0x798 mm/madvise.c:815
>  madvise_dontneed_free mm/madvise.c:929 [inline]
>  madvise_vma_behavior mm/madvise.c:1046 [inline]
>  madvise_walk_vmas mm/madvise.c:1268 [inline]
>  do_madvise+0x54c/0x2990 mm/madvise.c:1464
>  __do_sys_madvise mm/madvise.c:1481 [inline]
>  __se_sys_madvise mm/madvise.c:1479 [inline]
>  __arm64_sys_madvise+0x94/0xf8 mm/madvise.c:1479
>  __invoke_syscall arch/arm64/kernel/syscall.c:34 [inline]
>  invoke_syscall+0x8c/0x2e0 arch/arm64/kernel/syscall.c:48
>  el0_svc_common.constprop.0+0xec/0x2a8 arch/arm64/kernel/syscall.c:133
>  do_el0_svc+0x4c/0x70 arch/arm64/kernel/syscall.c:152
>  el0_svc+0x54/0x160 arch/arm64/kernel/entry-common.c:712
>  el0t_64_sync_handler+0x120/0x130 arch/arm64/kernel/entry-common.c:730
>  el0t_64_sync+0x1a4/0x1a8 arch/arm64/kernel/entry.S:598
>
> The buggy address belongs to the physical page:
> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x58c0d
> flags: 0x3fffe0000000000(node=0|zone=0|lastcpupid=0x1ffff)
> raw: 03fffe0000000000 fffffdffc0630388 fffffdffc071cc48 0000000000000000
> raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff000018c0cf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffff000018c0cf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> >ffff000018c0d000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>                    ^
>  ffff000018c0d080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>  ffff000018c0d100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> ==================================================================
>
>
> Syzkaller reproducer:
> # {Threaded:false Repeat:false RepeatTimes:0 Procs:1 Slowdown:1 Sandbox: SandboxArg:0 Leak:false NetInjection:false NetDevices:false NetReset:false Cgroups:false BinfmtMisc:false CloseFDs:false KCSAN:false DevlinkPCI:false NicVF:false USB:false VhciInjection:false Wifi:false IEEE802154:false Sysctl:false Swap:false UseTmpDir:false HandleSegv:false Trace:false LegacyOptions:{Collide:false Fault:false FaultCall:0 FaultNth:0}}
> madvise(&(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x17)
> mprotect(&(0x7f0000ffc000/0x4000)=nil, 0x4000, 0x0)
> mprotect(&(0x7f0000800000/0x800000)=nil, 0x800000, 0x1)
> madvise(&(0x7f0000400000/0xc00000)=nil, 0xc00000, 0x8)
>
>
> C reproducer:
> // autogenerated by syzkaller (https://github.com/google/syzkaller)
>
> #define _GNU_SOURCE
>
> #include <endian.h>
> #include <stdint.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <sys/syscall.h>
> #include <sys/types.h>
> #include <unistd.h>
>
> #ifndef __NR_madvise
> #define __NR_madvise 233
> #endif
> #ifndef __NR_mmap
> #define __NR_mmap 222
> #endif
> #ifndef __NR_mprotect
> #define __NR_mprotect 226
> #endif
>
> int main(void)
> {
>                 syscall(__NR_mmap, /*addr=*/0x1ffff000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/-1, /*offset=*/0ul);
>         syscall(__NR_mmap, /*addr=*/0x20000000ul, /*len=*/0x1000000ul, /*prot=PROT_WRITE|PROT_READ|PROT_EXEC*/7ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/-1, /*offset=*/0ul);
>         syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul, /*prot=*/0ul, /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/0x32ul, /*fd=*/-1, /*offset=*/0ul);
>                                 if (write(1, "executing program\n", sizeof("executing program\n") - 1)) {}
>         syscall(__NR_madvise, /*addr=*/0x20ffd000ul, /*len=*/0x3000ul, /*advice=MADV_POPULATE_WRITE*/0x17ul);
>         syscall(__NR_mprotect, /*addr=*/0x20ffc000ul, /*len=*/0x4000ul, /*prot=*/0ul);
>         syscall(__NR_mprotect, /*addr=*/0x20800000ul, /*len=*/0x800000ul, /*prot=PROT_READ*/1ul);
>         syscall(__NR_madvise, /*addr=*/0x20400000ul, /*len=*/0xc00000ul, /*advice=*/8ul);
>         return 0;
> }
>
>

Thanks
Barry

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