linux-kernel - [PATCH 0/2] Align kvrealloc() with krealloc()

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240717222427.2211-1-dakr@kernel.org>
Date: Thu, 18 Jul 2024 00:24:00 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: cl@...ux.com,
	penberg@...nel.org,
	rientjes@...gle.com,
	iamjoonsoo.kim@....com,
	akpm@...ux-foundation.org,
	vbabka@...e.cz,
	roman.gushchin@...ux.dev,
	42.hyeyoo@...il.com,
	urezki@...il.com,
	hch@...radead.org,
	kees@...nel.org,
	ojeda@...nel.org,
	wedsonaf@...il.com,
	mhocko@...nel.org,
	mpe@...erman.id.au,
	chandan.babu@...cle.com,
	christian.koenig@....com
Cc: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	rust-for-linux@...r.kernel.org,
	Danilo Krummrich <dakr@...nel.org>
Subject: [PATCH 0/2] Align kvrealloc() with krealloc()

Hi,

Besides the obvious (and desired) difference between krealloc() and kvrealloc(),
there is some inconsistency in their function signatures and behavior:

 - krealloc() frees the memory when the requested size is zero, whereas
   kvrealloc() simply returns a pointer to the existing allocation.

 - krealloc() behaves like kmalloc() if a NULL pointer is passed, whereas
   kvrealloc() does not accept a NULL pointer at all and, if passed, would fault
   instead.

 - krealloc() is self-contained, whereas kvrealloc() relies on the caller to
   provide the size of the previous allocation.

Inconsistent behavior throughout allocation APIs is error prone, hence make
kvrealloc() behave like krealloc(), which seems superior in all mentioned
aspects.

In order to be able to get rid of kvrealloc()'s oldsize parameter, introduce
vrealloc() and make use of it in kvrealloc().

Making use of vrealloc() in kvrealloc() also provides oppertunities to grow (and
shrink) allocations more efficiently. For instance, vrealloc() could be
optimized to extend the existing allocation if there is enough contiguous space
left in the virtual address space at the end of the existing allocation.

Besides the above, those functions are required by Rust's allocator abstractons
[1] (rework based on this series in [2]). With `Vec` or `KVec` respectively,
potentially growing (and shrinking) data structures are rather common.

The patches of this series can also be found in [3].

[1] https://lore.kernel.org/lkml/20240704170738.3621-1-dakr@redhat.com/
[2] https://git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=rust/mm
[3] https://git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=mm/krealloc

Danilo Krummrich (2):
  mm: vmalloc: implement vrealloc()
  mm: kvmalloc: align kvrealloc() with krealloc()

 arch/powerpc/platforms/pseries/papr-vpd.c |  5 +-
 drivers/gpu/drm/drm_exec.c                |  3 +-
 fs/xfs/xfs_log_recover.c                  |  2 +-
 include/linux/slab.h                      |  3 +-
 include/linux/vmalloc.h                   |  4 ++
 kernel/resource.c                         |  3 +-
 lib/fortify_kunit.c                       |  3 +-
 mm/util.c                                 | 72 ++++++++++++++++-------
 mm/vmalloc.c                              | 58 ++++++++++++++++++
 9 files changed, 118 insertions(+), 35 deletions(-)

base-commit: 51835949dda3783d4639cfa74ce13a3c9829de00
-- 
2.45.2