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    SubjectRe: [PATCH] kernel: sysctl: use 'unsigned long' type for 'zero' variable
    On Wed, 3 Dec 2014, Andrey Ryabinin wrote:

    >
    > Commit ed4d4902ebdd ("mm, hugetlb: remove hugetlb_zero and hugetlb_infinity") replaced
    > 'unsigned long hugetlb_zero' with 'int zero' leading to out-of-bounds access
    > in proc_doulongvec_minmax():
    >
    > ==================================================================
    > BUG: AddressSanitizer: out of bounds access in
    > __do_proc_doulongvec_minmax+0x8a0/0x9a0 at addr ffffffff83980960
    > Read of size 8 by task trinity-c14/6919
    > Out-of-bounds access to the global variable 'zero'
    > [ffffffff83980960-ffffffff83980964) defined at ipc/ipc_sysctl.c:158
    >
    > CPU: 1 PID: 6919 Comm: trinity-c14 Not tainted 3.18.0-rc1+ #50
    > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
    > 0000000000000001 ffff8800b68cf418 ffffffff82c2d3ae 0000000000000000
    > ffff8800b68cf4c0 ffff8800b68cf4a8 ffffffff813eaa81 ffffffff0000000c
    > ffff88010b003600 ffff8800b68cf479 0000000000000296 0000000000000000
    > Call Trace:
    > [<ffffffff813ead71>] __asan_report_load8_noabort+0x51/0x70
    > mm/kasan/report.c:248
    > [<ffffffff810cc3e0>] __do_proc_doulongvec_minmax+0x8a0/0x9a0
    > kernel/sysctl.c:2284
    > [< inlined >] proc_doulongvec_minmax+0x50/0x80
    > do_proc_doulongvec_minmax kernel/sysctl.c:2322
    > [<ffffffff810cc530>] proc_doulongvec_minmax+0x50/0x80 kernel/sysctl.c:2345
    > [<ffffffff813c9e5a>] hugetlb_sysctl_handler_common+0x12a/0x3c0
    > mm/hugetlb.c:2270
    > [<ffffffff813cb45c>] hugetlb_mempolicy_sysctl_handler+0x1c/0x20
    > mm/hugetlb.c:2293
    > [<ffffffff8153e6e9>] proc_sys_call_handler+0x179/0x1f0
    > fs/proc/proc_sysctl.c:506
    > [<ffffffff8153e76f>] proc_sys_write+0xf/0x20 fs/proc/proc_sysctl.c:524
    > [<ffffffff813f1563>] __kernel_write+0x123/0x440 fs/read_write.c:502
    > [<ffffffff8147ebaa>] write_pipe_buf+0x14a/0x1d0 fs/splice.c:1074
    > [< inlined >] __splice_from_pipe+0x22e/0x6f0
    > splice_from_pipe_feed fs/splice.c:769
    > [<ffffffff8147dbde>] __splice_from_pipe+0x22e/0x6f0 fs/splice.c:886
    > [<ffffffff81483211>] splice_from_pipe+0xc1/0x110 fs/splice.c:921
    > [<ffffffff81483298>] default_file_splice_write+0x18/0x50 fs/splice.c:1086
    > [< inlined >] direct_splice_actor+0x104/0x1c0 do_splice_from
    > fs/splice.c:1128
    > [<ffffffff8147cfc4>] direct_splice_actor+0x104/0x1c0 fs/splice.c:1284
    > [<ffffffff8147e5ba>] splice_direct_to_actor+0x24a/0x6f0 fs/splice.c:1237
    > [<ffffffff81483424>] do_splice_direct+0x154/0x270 fs/splice.c:1327
    > [<ffffffff813f3bfb>] do_sendfile+0x5fb/0x1260 fs/read_write.c:1266
    > [< inlined >] SyS_sendfile64+0xfa/0x100 SYSC_sendfile64
    > fs/read_write.c:1327
    > [<ffffffff813f6bea>] SyS_sendfile64+0xfa/0x100 fs/read_write.c:1313
    > [<ffffffff82c464f9>] ia32_do_call+0x13/0x13 arch/x86/ia32/ia32entry.S:444
    > Memory state around the buggy address:
    > ffffffff83980680: 04 f8 f8 f8 f8 f8 f8 f8 02 f8 f8 f8 f8 f8 f8 f8
    > ffffffff83980700: 00 f8 f8 f8 f8 f8 f8 f8 00 f8 f8 f8 f8 f8 f8 f8
    > ffffffff83980780: 00 00 00 00 00 00 00 00 f8 f8 f8 f8 00 00 00 00
    > ffffffff83980800: 00 00 00 00 00 00 00 00 f8 f8 f8 f8 04 f8 f8 f8
    > ffffffff83980880: f8 f8 f8 f8 04 f8 f8 f8 f8 f8 f8 f8 04 f8 f8 f8
    > >ffffffff83980900: f8 f8 f8 f8 04 f8 f8 f8 f8 f8 f8 f8 04 f8 f8 f8
    > ^
    > ffffffff83980980: f8 f8 f8 f8 00 00 00 00 f8 f8 f8 f8 00 00 00 00
    > ffffffff83980a00: 02 f8 f8 f8 f8 f8 f8 f8 00 00 00 00 00 00 00 00
    > ffffffff83980a80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    > ffffffff83980b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    > ffffffff83980b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    > ==================================================================
    >
    > Use the 'unsigned long' type for 'zero' variable to fix this.
    > Changing type to 'unsigned long' shouldn't affect any other users
    > of this variable.
    >
    > Reported-by: Dmitry Vyukov <dvyukov@google.com>
    > Fixes: ed4d4902ebdd ("mm, hugetlb: remove hugetlb_zero and hugetlb_infinity")
    > Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
    > ---
    > kernel/sysctl.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/kernel/sysctl.c b/kernel/sysctl.c
    > index 15f2511..45c45c9 100644
    > --- a/kernel/sysctl.c
    > +++ b/kernel/sysctl.c
    > @@ -120,7 +120,7 @@ static int sixty = 60;
    >
    > static int __maybe_unused neg_one = -1;
    >
    > -static int zero;
    > +static unsigned long zero;
    > static int __maybe_unused one = 1;
    > static int __maybe_unused two = 2;
    > static int __maybe_unused four = 4;

    __do_proc_doulongvec_minmax() casts both extra1 and extra2 to unsigned
    long *, so this is appropriate.

    Acked-by: David Rientjes <rientjes@google.com>


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