Re: git: 21e45c30c35c - main - mmap(MAP_STACK): on stack grow, use original protection
Date: Thu, 20 Jul 2023 18:09:26 UTC
This email appears truncated. My original reply was,
Yes, this fixes the screen and pkg regressions.
Thanks for the patch.
--
Cheers,
Cy Schubert <Cy.Schubert@cschubert.com>
FreeBSD UNIX: <cy@FreeBSD.org> Web: https://FreeBSD.org
NTP: <cy@nwtime.org> Web: https://nwtime.org
e^(i*pi)+1=0
In message <20230720180230.18BDF11F@slippy.cwsent.com>, Cy Schubert writes:
> In message <ZLlwK0sM57aoE-cr@kib.kiev.ua>, Konstantin Belousov writes:
> > On Thu, Jul 20, 2023 at 10:06:24AM -0700, Cy Schubert wrote:
> > > In message <20230720164145.0CF1311F@slippy.cwsent.com>, Cy Schubert write
> s:
> > > > In message <20230720163231.B1D4277@slippy.cwsent.com>, Cy Schubert writ
> es
> > :
> > > > > In message <202307201412.36KECDSU084918@gitrepo.freebsd.org>, Konstan
> ti
> > n
> > > > > Belous
> > > > > ov writes:
> > > > > > The branch main has been updated by kib:
> > > > > >
> > > > > > URL: https://cgit.FreeBSD.org/src/commit/?id=21e45c30c35c9aa732073f
> 72
> > 5924
> > > > ca
> > > > > f5
> > > > > > 81c93460
> > > > > >
> > > > > > commit 21e45c30c35c9aa732073f725924caf581c93460
> > > > > > Author: Konstantin Belousov <kib@FreeBSD.org>
> > > > > > AuthorDate: 2023-07-19 11:05:32 +0000
> > > > > > Commit: Konstantin Belousov <kib@FreeBSD.org>
> > > > > > CommitDate: 2023-07-20 14:11:42 +0000
> > > > > >
> > > > > > mmap(MAP_STACK): on stack grow, use original protection
> > > > > >
> > > > > > If mprotect(2) changed protection in the bottom of the currentl
> y
> > grow
> > > > n
> > > > > > stack region, currently the changed protection would be used fo
> r
> > the
> > > > > > stack grow on next fault. This is arguably unexpected.
> > > > > >
> > > > > > Store the original protection for the entry at mmap(2) time in
> th
> > e
> > > > > > offset member of the gap vm_map_entry, and use it for protectio
> n
> > of t
> > > > he
> > > > > > grown stack region.
> > > > > >
> > > > > > PR: 272585
> > > > > > Reported by: John F. Carr <jfc@mit.edu>
> > > > > > Reviewed by: alc, markj
> > > > > > Sponsored by: The FreeBSD Foundation
> > > > > > MFC after: 1 week
> > > > > > Differential revision: https://reviews.freebsd.org/D41089
> > > > > > ---
> > > > > > sys/vm/vm_map.c | 24 ++++++++++++++++--------
> > > > > > sys/vm/vm_map.h | 4 ++++
> > > > > > 2 files changed, 20 insertions(+), 8 deletions(-)
> > > > > >
> > > > > > diff --git a/sys/vm/vm_map.c b/sys/vm/vm_map.c
> > > > > > index a02107b5e64d..997a49111a59 100644
> > > > > > --- a/sys/vm/vm_map.c
> > > > > > +++ b/sys/vm/vm_map.c
> > > > > > @@ -4493,7 +4493,7 @@ static int
> > > > > > vm_map_stack_locked(vm_map_t map, vm_offset_t addrbos, vm_size_t m
> ax
> > _ssi
> > > > ze
> > > > > ,
> > > > > > vm_size_t growsize, vm_prot_t prot, vm_prot_t max, int cow)
> > > > > > {
> > > > > > - vm_map_entry_t new_entry, prev_entry;
> > > > > > + vm_map_entry_t gap_entry, new_entry, prev_entry;
> > > > > > vm_offset_t bot, gap_bot, gap_top, top;
> > > > > > vm_size_t init_ssize, sgp;
> > > > > > int orient, rv;
> > > > > > @@ -4575,11 +4575,14 @@ vm_map_stack_locked(vm_map_t map, vm_offset
> _t
> > add
> > > > rb
> > > > > os
> > > > > > , vm_size_t max_ssize,
> > > > > > * read-ahead logic is never used for it. Re-use
> > > > > > * next_read of the gap entry to store
> > > > > > * stack_guard_page for vm_map_growstack().
> > > > > > + * Similarly, since a gap cannot have a backing object,
> > > > > > + * store the original stack protections in the
> > > > > > + * object offset.
> > > > > > */
> > > > > > - if (orient == MAP_STACK_GROWS_DOWN)
> > > > > > - vm_map_entry_pred(new_entry)->next_read = sgp;
> > > > > > - else
> > > > > > - vm_map_entry_succ(new_entry)->next_read = sgp;
> > > > > > + gap_entry = orient == MAP_STACK_GROWS_DOWN ?
> > > > > > + vm_map_entry_pred(new_entry) : vm_map_entry_succ(ne
> > w_entry)
> > > > > > ;
> > > > > > + gap_entry->next_read = sgp;
> > > > > > + gap_entry->offset = prot;
> > > > > > } else {
> > > > > > (void)vm_map_delete(map, bot, top);
> > > > > > }
> > > > > > @@ -4599,6 +4602,7 @@ vm_map_growstack(vm_map_t map, vm_offset_t ad
> dr
> > , vm
> > > > _m
> > > > > ap
> > > > > > _entry_t gap_entry)
> > > > > > struct ucred *cred;
> > > > > > vm_offset_t gap_end, gap_start, grow_start;
> > > > > > vm_size_t grow_amount, guard, max_grow;
> > > > > > + vm_prot_t prot;
> > > > > > rlim_t lmemlim, stacklim, vmemlim;
> > > > > > int rv, rv1 __diagused;
> > > > > > bool gap_deleted, grow_down, is_procstack;
> > > > > > @@ -4739,6 +4743,12 @@ retry:
> > > > > > }
> > > > > >
> > > > > > if (grow_down) {
> > > > > > + /*
> > > > > > + * The gap_entry "offset" field is overloaded. See
> > > > > > + * vm_map_stack_locked().
> > > > > > + */
> > > > > > + prot = gap_entry->offset;
> > > > > > +
> > > > > > grow_start = gap_entry->end - grow_amount;
> > > > > > if (gap_entry->start + grow_amount == gap_entry->end) {
> > > > > > gap_start = gap_entry->start;
> > > > > > @@ -4751,9 +4761,7 @@ retry:
> > > > > > gap_deleted = false;
> > > > > > }
> > > > > > rv = vm_map_insert(map, NULL, 0, grow_start,
> > > > > > - grow_start + grow_amount,
> > > > > > - stack_entry->protection, stack_entry->max_protectio
> > n,
> > > > > > - MAP_STACK_GROWS_DOWN);
> > > > > > + grow_start + grow_amount, prot, prot, MAP_STACK_GRO
> > WS_DOWN)
> > > > > > ;
> > > > > > if (rv != KERN_SUCCESS) {
> > > > > > if (gap_deleted) {
> > > > > > rv1 = vm_map_insert(map, NULL, 0, gap_s
> > tart,
> > > > > > diff --git a/sys/vm/vm_map.h b/sys/vm/vm_map.h
> > > > > > index fd8b606e8ddc..c4ed36ce57ba 100644
> > > > > > --- a/sys/vm/vm_map.h
> > > > > > +++ b/sys/vm/vm_map.h
> > > > > > @@ -97,6 +97,10 @@ union vm_map_object {
> > > > > > * a VM object (or sharing map) and offset into that object,
> > > > > > * and user-exported inheritance and protection information.
> > > > > > * Also included is control information for virtual copy operation
> > > > s.
> > > > > > + *
> > > > > > + * For stack gap map entries (MAP_ENTRY_GUARD | MAP_ENTRY_GROWS_DO
> > > > WN
> > > > > > + * or UP), the next_read member is reused as the stack_guard_page
> > > > > > + * storage, and offset is the stack protection.
> > > > > > */
> > > > > > struct vm_map_entry {
> > > > > > struct vm_map_entry *left; /* left child or previous entry
> > */
> > > > > >
> > > > >
> > > > > This commit has caused screen (sysutils/screen) to display the follow
> in
> > g
> > > > > error when opening a new screen window (ctrl-A c):
> > > > >
> > > > > pid 28473 comm screen-4.9.0 has trashed its stack, killing
> > > > >
> > > > >
> > > > > --
> > > > > Cheers,
> > > > > Cy Schubert <Cy.Schubert@cschubert.com>
> > > > > FreeBSD UNIX: <cy@FreeBSD.org> Web: https://FreeBSD.org
> > > > > NTP: <cy@nwtime.org> Web: https://nwtime.org
> > > > >
> > > > > e^(i*pi)+1=0
> > > > >
> > > > >
> > > >
> > > > I'm also seeing artifacts in emails by nmh