Commit 44f65d9006 ("binfmt_elf: mseal address zero") unconditionally
provided do_mseal() to any internal kernel caller in order to address a
corner case slated for possible removal.
It also incorrectly attempts to mseal without checking to see whether the
mapping even succeeded.
Restrict the scope to the corner case by providing mseal_mmap_page_zero()
which asserts the MMAP_PAGE_ZERO personality.
Avoid unnecessary checks in the start, end range by abstracting the actual
mseal()'ing to mseal_range() and have mseal_mmap_page_zero() call that
instead.
Also only try to seal the VMA if we mapped the VMA. This isn't strictly
necessary as the operation would error out anyway, but it's useless work
and could be problematic if me make future changes to mseal semantics.
Link: https://lore.kernel.org/20260717-mseal-fixups-v2-2-0daa0014b813@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
4c1c2d2418