[Bug 272585] calling mprotect in an mmap-ed stack can affect non-target pages

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=272585

--- Comment #2 from commit-hook@FreeBSD.org ---
A commit in branch main references this bug:

URL:
https://cgit.FreeBSD.org/src/commit/?id=21e45c30c35c9aa732073f725924caf581c93460

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 currently grown
    stack region, currently the changed protection would be used for the
    stack grow on next fault.  This is arguably unexpected.

    Store the original protection for the entry at mmap(2) time in the
    offset member of the gap vm_map_entry, and use it for protection of the
    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(-)

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