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Zev Weiss d5aad4c2ca prctl: generalize PR_SET_MDWE support check to be per-arch 
Patch series "ARM: prctl: Reject PR_SET_MDWE where not supported".

I noticed after a recent kernel update that my ARM926 system started
segfaulting on any execve() after calling prctl(PR_SET_MDWE).  After some
investigation it appears that ARMv5 is incapable of providing the
appropriate protections for MDWE, since any readable memory is also
implicitly executable.

The prctl_set_mdwe() function already had some special-case logic added
disabling it on PARISC (commit 793838138c, "prctl: Disable
prctl(PR_SET_MDWE) on parisc"); this patch series (1) generalizes that
check to use an arch_*() function, and (2) adds a corresponding override
for ARM to disable MDWE on pre-ARMv6 CPUs.

With the series applied, prctl(PR_SET_MDWE) is rejected on ARMv5 and
subsequent execve() calls (as well as mmap(PROT_READ|PROT_WRITE)) can
succeed instead of unconditionally failing; on ARMv6 the prctl works as it
did previously.

[0] https://lore.kernel.org/all/2023112456-linked-nape-bf19@gregkh/


This patch (of 2):

There exist systems other than PARISC where MDWE may not be feasible to
support; rather than cluttering up the generic code with additional
arch-specific logic let's add a generic function for checking MDWE support
and allow each arch to override it as needed.

Link: https://lkml.kernel.org/r/20240227013546.15769-4-zev@bewilderbeest.net
Link: https://lkml.kernel.org/r/20240227013546.15769-5-zev@bewilderbeest.net
Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Acked-by: Helge Deller <deller@gmx.de>	[parisc]
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Florent Revest <revest@chromium.org>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ondrej Mosnacek <omosnace@redhat.com>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Russell King (Oracle) <linux@armlinux.org.uk>
Cc: Sam James <sam@gentoo.org>
Cc: Stefan Roesch <shr@devkernel.io>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Cc: <stable@vger.kernel.org>	[6.3+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 		2024-03-26 11:07:22 -07:00
..
boot parisc: Allow building uncompressed Linux kernel 2023-10-30 14:54:40 +01:00
configs staging: qlge: Retire the driver 2023-10-21 11:52:54 +02:00
include prctl: generalize PR_SET_MDWE support check to be per-arch 2024-03-26 11:07:22 -07:00
kernel parisc/unaligned: Rewrite 64-bit inline assembly of emulate_ldd() 2024-02-27 22:51:44 +01:00
lib parisc: ucmpdi2: Fix no previous prototype for '__ucmpdi2' warning 2023-08-10 18:34:05 +02:00
math-emu parisc: avoid c23 'nullptr' idenitifier 2024-02-27 22:51:44 +01:00
mm parisc: Fix random data corruption from exception handler 2024-01-30 17:18:58 +01:00
net parisc: Add eBPF JIT compiler glue code and Makefile 2023-08-22 10:24:47 +02:00
video arch/parisc: Detect primary video device from device instance 2024-01-12 12:38:37 +01:00
Kbuild parisc: Wire up eBPF JIT compiler 2023-08-22 10:24:47 +02:00
Kconfig Kbuild updates for v6.9 2024-03-21 14:41:00 -07:00
Kconfig.debug parisc: Use page table locks only if DEBUG_KERNEL is enabled 2023-08-20 20:23:46 +02:00
Makefile kbuild: use 4-space indentation when followed by conditionals 2024-02-15 06:05:44 +09:00
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