01.09.2017 16:53, Dmitry V. Levin P?P8QP5Q: > On Fri, Sep 01, 2017 at 12:15:17PM +0300, Stanislav Kinsburskiy wrote: >> 31.08.2017 20:22, Dmitry V. Levin P?P8QP5Q: >>> On Thu, Aug 31, 2017 at 05:57:11PM +0400, Stanislav Kinsburskiy wrote: >>>> The structure autofs_v5_packet (except name) is not aligned by 8 bytes, >>>> which >>>> lead to different sizes in 32 and 64-bit architectures. >>>> Let's form 32-bit compatible packet when daemon has 32-bit addressation. >>>> >>>> Signed-off-by: Stanislav Kinsburskiy <skinsbur...@virtuozzo.com> >>>> --- >>>> fs/autofs4/waitq.c | 11 +++++++++-- >>>> 1 file changed, 9 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c >>>> index 309ca6b..484cf2e 100644 >>>> --- a/fs/autofs4/waitq.c >>>> +++ b/fs/autofs4/waitq.c >>>> @@ -153,12 +153,19 @@ static void autofs4_notify_daemon(struct >>>> autofs_sb_info *sbi, >>>> { >>>> struct autofs_v5_packet *packet = &pkt.v5_pkt.v5_packet; >>>> struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns; >>>> + size_t name_offset; >>>> >>>> - pktsz = sizeof(*packet); >>>> + if (sbi->is32bit) >>>> + name_offset = offsetof(struct autofs_v5_packet, len) + >>>> + sizeof(packet->len); >>>> + else >>>> + name_offset = offsetof(struct autofs_v5_packet, name); >>> >>> This doesn't help at all because the offset of struct autofs_v5_packet.name >>> does not change. >>> >>>> + pktsz = name_offset + sizeof(packet->name); >>> >>> What changes is pktsz: it's either sizeof(struct autofs_v5_packet) >>> or 4 bytes less, depending on the architecture. >> >> Indeed. Thanks! >> >>> For example, >>> >>> #ifdef CONFIG_COMPAT >>> if (__alignof__(compat_u64) < __alignof__(u64) && sbi->is32bit) >> >> Unfortunately I don't get this "alignof" checks. >> The intention of "is32bit" was to define this compat case completely. >> Why are they required? > > On some 32-bit architectures like arm, u64 is 64-bit aligned, on others > like x86 it is not. This alignof check ensures that compat 32-bit > architectures with 64-bit alignment are not going to be broken > by the change. >
Thanks for the explanation! But looks like the issue is hidden so deep (thanks to O_DIRECT), that becomes unimportant. > > > > _______________________________________________ > Devel mailing list > Devel@openvz.org > https://lists.openvz.org/mailman/listinfo/devel > _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel