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References: <20171126063117.oytmra3tqoj5546u@wfg-t540p.sh.intel.com>
 <20171127210301.GA55812@localhost.corp.microsoft.com> <20171128124534.3jvuala525wvn64r@wfg-t540p.sh.intel.com>
 <20171129175430.GA58181@big-sky.attlocal.net>
From: Dmitry Vyukov <dvyukov@google.com>
Date: Thu, 30 Nov 2017 10:59:05 +0100
Message-ID: <CACT4Y+bji1JMJVJZdv=+bD8JZ1kqrmJ0PWXvHdYzRFcnAKDSGw@mail.gmail.com>
Subject: Re: [pcpu] BUG: KASAN: use-after-scope in pcpu_setup_first_chunk+0x1e3b/0x29e2
To: Dennis Zhou <dennisszhou@gmail.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Kees Cook <keescook@chromium.org>, Linux-MM <linux-mm@kvack.org>,
        Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Josef Bacik <jbacik@fb.com>, LKML <linux-kernel@vger.kernel.org>,
        LKP <lkp@01.org>, Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Mark Rutland <mark.rutland@arm.com>
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On Wed, Nov 29, 2017 at 6:54 PM, Dennis Zhou <dennisszhou@gmail.com> wrote:
> Hi everyone,
>
> I spent a bit of time learning more about this problem as Fengguang was
> able to determine the root commit f7dd2507893cc3. I reproduced the bug
> in userspace to make life a bit easier and below the assignment occurs
> before the unpoison. This is fine if we're sequentially proceeding, but
> as in the case in percpu, it's calling the function in a for loop
> causing the assignment to happen after it has been poisoned in the prior
> iteration.
>
> <bb 3> [0.00%]:
>   _1 = (long unsigned int) i_4;
>   _2 = _1 * 16;
>   _3 = p_8 + _2;
>   list_14 = _3;
>   __u = {};
>   ASAN_MARK (UNPOISON, &__u, 8);
>   __u.__val = list_14;
>
> <bb 9> [0.00%]:
>   _24 = __u.__val;
>   ASAN_MARK (POISON, &__u, 8);
>   list_14->prev = list_14;
>   i_13 = i_4 + 1;
>
> <bb 10> [0.00%]:
>   # i_4 = PHI <i_9(2), i_13(9)>
>   if (i_4 <= 9)
>     goto <bb 3>; [0.00%]
>   else
>     goto <bb 11>; [0.00%]
>
> I don't know how to go about fixing this though. The reproducing code is
> below and was compiled with gcc-7 and the structleak_plugin.


Are we sure that structleak plugin is not at fault? If yes, then we
need to report this to https://gcc.gnu.org/bugzilla/ with instructions
on how to build/use the plugin.


> I hope this helps.
>
> Thanks,
> Dennis
>
> ----
> #include <stdint.h>
> #include <stdlib.h>
>
> #define barrier()
>
> #define WRITE_ONCE(x, val) \
> ({                                                      \
>         union { typeof(x) __val; char __c[1]; } __u =   \
>                 { .__val = (typeof(x)) (val) }; \
>         __write_once_size(&(x), __u.__c, sizeof(x));    \
>         __u.__val;                                      \
> })
>
> typedef         uint8_t         __u8;
> typedef         uint16_t        __u16;
> typedef         uint32_t        __u32;
> typedef         uint64_t        __u64;
>
> static inline __attribute__((always_inline)) void __write_once_size(volatile void *p, void *res, int size)
> {
>         switch (size) {
>         case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
>         case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
>         case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
>         case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
>         default:
>                 barrier();
>                 __builtin_memcpy((void *)p, (const void *)res, size);
>                 barrier();
>         }
> }
>
> struct list_head {
>         struct list_head *next, *prev;
> };
>
> static inline __attribute__((always_inline)) void INIT_LIST_HEAD(struct list_head *list)
> {
>         WRITE_ONCE(list->next, list);
>         list->prev = list;
> }
>
> int main(int argc, char *argv[])
> {
>         struct list_head *p = malloc(10 * sizeof(struct list_head));
>         int i;
>
>         for (i = 0; i < 10; i++) {
>                 INIT_LIST_HEAD(&p[i]);
>         }
>
>         free(p);
>
>         return 0;
> }

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References: <20171126063117.oytmra3tqoj5546u@wfg-t540p.sh.intel.com>
 <20171127210301.GA55812@localhost.corp.microsoft.com> <20171128124534.3jvuala525wvn64r@wfg-t540p.sh.intel.com>
 <20171129175430.GA58181@big-sky.attlocal.net>
From: Dmitry Vyukov <dvyukov@google.com>
Date: Thu, 30 Nov 2017 10:59:05 +0100
Message-ID: <CACT4Y+bji1JMJVJZdv=+bD8JZ1kqrmJ0PWXvHdYzRFcnAKDSGw@mail.gmail.com>
Subject: Re: [pcpu] BUG: KASAN: use-after-scope in pcpu_setup_first_chunk+0x1e3b/0x29e2
Content-Type: text/plain; charset="UTF-8"
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Dennis Zhou <dennisszhou@gmail.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, Kees Cook <keescook@chromium.org>, Linux-MM <linux-mm@kvack.org>, Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>, Linus Torvalds <torvalds@linux-foundation.org>, Josef Bacik <jbacik@fb.com>, LKML <linux-kernel@vger.kernel.org>, LKP <lkp@01.org>, Andrey Ryabinin <aryabinin@virtuozzo.com>, Mark Rutland <mark.rutland@arm.com>

On Wed, Nov 29, 2017 at 6:54 PM, Dennis Zhou <dennisszhou@gmail.com> wrote:
> Hi everyone,
>
> I spent a bit of time learning more about this problem as Fengguang was
> able to determine the root commit f7dd2507893cc3. I reproduced the bug
> in userspace to make life a bit easier and below the assignment occurs
> before the unpoison. This is fine if we're sequentially proceeding, but
> as in the case in percpu, it's calling the function in a for loop
> causing the assignment to happen after it has been poisoned in the prior
> iteration.
>
> <bb 3> [0.00%]:
>   _1 = (long unsigned int) i_4;
>   _2 = _1 * 16;
>   _3 = p_8 + _2;
>   list_14 = _3;
>   __u = {};
>   ASAN_MARK (UNPOISON, &__u, 8);
>   __u.__val = list_14;
>
> <bb 9> [0.00%]:
>   _24 = __u.__val;
>   ASAN_MARK (POISON, &__u, 8);
>   list_14->prev = list_14;
>   i_13 = i_4 + 1;
>
> <bb 10> [0.00%]:
>   # i_4 = PHI <i_9(2), i_13(9)>
>   if (i_4 <= 9)
>     goto <bb 3>; [0.00%]
>   else
>     goto <bb 11>; [0.00%]
>
> I don't know how to go about fixing this though. The reproducing code is
> below and was compiled with gcc-7 and the structleak_plugin.


Are we sure that structleak plugin is not at fault? If yes, then we
need to report this to https://gcc.gnu.org/bugzilla/ with instructions
on how to build/use the plugin.


> I hope this helps.
>
> Thanks,
> Dennis
>
> ----
> #include <stdint.h>
> #include <stdlib.h>
>
> #define barrier()
>
> #define WRITE_ONCE(x, val) \
> ({                                                      \
>         union { typeof(x) __val; char __c[1]; } __u =   \
>                 { .__val = (typeof(x)) (val) }; \
>         __write_once_size(&(x), __u.__c, sizeof(x));    \
>         __u.__val;                                      \
> })
>
> typedef         uint8_t         __u8;
> typedef         uint16_t        __u16;
> typedef         uint32_t        __u32;
> typedef         uint64_t        __u64;
>
> static inline __attribute__((always_inline)) void __write_once_size(volatile void *p, void *res, int size)
> {
>         switch (size) {
>         case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
>         case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
>         case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
>         case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
>         default:
>                 barrier();
>                 __builtin_memcpy((void *)p, (const void *)res, size);
>                 barrier();
>         }
> }
>
> struct list_head {
>         struct list_head *next, *prev;
> };
>
> static inline __attribute__((always_inline)) void INIT_LIST_HEAD(struct list_head *list)
> {
>         WRITE_ONCE(list->next, list);
>         list->prev = list;
> }
>
> int main(int argc, char *argv[])
> {
>         struct list_head *p = malloc(10 * sizeof(struct list_head));
>         int i;
>
>         for (i = 0; i < 10; i++) {
>                 INIT_LIST_HEAD(&p[i]);
>         }
>
>         free(p);
>
>         return 0;
> }

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From mboxrd@z Thu Jan  1 00:00:00 1970
Content-Type: multipart/mixed; boundary="===============4509590115725709728=="
MIME-Version: 1.0
From: Dmitry Vyukov <dvyukov@google.com>
To: lkp@lists.01.org
Subject: Re: [pcpu] BUG: KASAN: use-after-scope in pcpu_setup_first_chunk+0x1e3b/0x29e2
Date: Thu, 30 Nov 2017 10:59:05 +0100
Message-ID: <CACT4Y+bji1JMJVJZdv=+bD8JZ1kqrmJ0PWXvHdYzRFcnAKDSGw@mail.gmail.com>
In-Reply-To: <20171129175430.GA58181@big-sky.attlocal.net>
List-Id: <oe-lkp.lists.linux.dev>

--===============4509590115725709728==
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable

On Wed, Nov 29, 2017 at 6:54 PM, Dennis Zhou <dennisszhou@gmail.com> wrot=
e:
> Hi everyone,
>
> I spent a bit of time learning more about this problem as Fengguang was
> able to determine the root commit f7dd2507893cc3. I reproduced the bug
> in userspace to make life a bit easier and below the assignment occurs
> before the unpoison. This is fine if we're sequentially proceeding, but
> as in the case in percpu, it's calling the function in a for loop
> causing the assignment to happen after it has been poisoned in the prior
> iteration.
>
> <bb 3> [0.00%]:
>   _1 =3D (long unsigned int) i_4;
>   _2 =3D _1 * 16;
>   _3 =3D p_8 + _2;
>   list_14 =3D _3;
>   __u =3D {};
>   ASAN_MARK (UNPOISON, &__u, 8);
>   __u.__val =3D list_14;
>
> <bb 9> [0.00%]:
>   _24 =3D __u.__val;
>   ASAN_MARK (POISON, &__u, 8);
>   list_14->prev =3D list_14;
>   i_13 =3D i_4 + 1;
>
> <bb 10> [0.00%]:
>   # i_4 =3D PHI <i_9(2), i_13(9)>
>   if (i_4 <=3D 9)
>     goto <bb 3>; [0.00%]
>   else
>     goto <bb 11>; [0.00%]
>
> I don't know how to go about fixing this though. The reproducing code is
> below and was compiled with gcc-7 and the structleak_plugin.


Are we sure that structleak plugin is not at fault? If yes, then we
need to report this to https://gcc.gnu.org/bugzilla/ with instructions
on how to build/use the plugin.


> I hope this helps.
>
> Thanks,
> Dennis
>
> ----
> #include <stdint.h>
> #include <stdlib.h>
>
> #define barrier()
>
> #define WRITE_ONCE(x, val) \
> ({                                                      \
>         union { typeof(x) __val; char __c[1]; } __u =3D   \
>                 { .__val =3D (typeof(x)) (val) }; \
>         __write_once_size(&(x), __u.__c, sizeof(x));    \
>         __u.__val;                                      \
> })
>
> typedef         uint8_t         __u8;
> typedef         uint16_t        __u16;
> typedef         uint32_t        __u32;
> typedef         uint64_t        __u64;
>
> static inline __attribute__((always_inline)) void __write_once_size(volat=
ile void *p, void *res, int size)
> {
>         switch (size) {
>         case 1: *(volatile __u8 *)p =3D *(__u8 *)res; break;
>         case 2: *(volatile __u16 *)p =3D *(__u16 *)res; break;
>         case 4: *(volatile __u32 *)p =3D *(__u32 *)res; break;
>         case 8: *(volatile __u64 *)p =3D *(__u64 *)res; break;
>         default:
>                 barrier();
>                 __builtin_memcpy((void *)p, (const void *)res, size);
>                 barrier();
>         }
> }
>
> struct list_head {
>         struct list_head *next, *prev;
> };
>
> static inline __attribute__((always_inline)) void INIT_LIST_HEAD(struct l=
ist_head *list)
> {
>         WRITE_ONCE(list->next, list);
>         list->prev =3D list;
> }
>
> int main(int argc, char *argv[])
> {
>         struct list_head *p =3D malloc(10 * sizeof(struct list_head));
>         int i;
>
>         for (i =3D 0; i < 10; i++) {
>                 INIT_LIST_HEAD(&p[i]);
>         }
>
>         free(p);
>
>         return 0;
> }

--===============4509590115725709728==--