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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>
This commit is contained in:
parent
db09f2df91
commit
d5aad4c2ca
14
arch/parisc/include/asm/mman.h
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14
arch/parisc/include/asm/mman.h
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@ -0,0 +1,14 @@
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __ASM_MMAN_H__
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#define __ASM_MMAN_H__
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#include <uapi/asm/mman.h>
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/* PARISC cannot allow mdwe as it needs writable stacks */
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static inline bool arch_memory_deny_write_exec_supported(void)
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{
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return false;
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}
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#define arch_memory_deny_write_exec_supported arch_memory_deny_write_exec_supported
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#endif /* __ASM_MMAN_H__ */
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@ -162,6 +162,14 @@ calc_vm_flag_bits(unsigned long flags)
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unsigned long vm_commit_limit(void);
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unsigned long vm_commit_limit(void);
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#ifndef arch_memory_deny_write_exec_supported
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static inline bool arch_memory_deny_write_exec_supported(void)
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{
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return true;
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}
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#define arch_memory_deny_write_exec_supported arch_memory_deny_write_exec_supported
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#endif
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/*
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/*
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* Denies creating a writable executable mapping or gaining executable permissions.
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* Denies creating a writable executable mapping or gaining executable permissions.
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*
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*
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@ -2408,8 +2408,11 @@ static inline int prctl_set_mdwe(unsigned long bits, unsigned long arg3,
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if (bits & PR_MDWE_NO_INHERIT && !(bits & PR_MDWE_REFUSE_EXEC_GAIN))
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if (bits & PR_MDWE_NO_INHERIT && !(bits & PR_MDWE_REFUSE_EXEC_GAIN))
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return -EINVAL;
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return -EINVAL;
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/* PARISC cannot allow mdwe as it needs writable stacks */
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/*
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if (IS_ENABLED(CONFIG_PARISC))
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* EOPNOTSUPP might be more appropriate here in principle, but
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* existing userspace depends on EINVAL specifically.
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*/
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if (!arch_memory_deny_write_exec_supported())
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return -EINVAL;
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return -EINVAL;
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current_bits = get_current_mdwe();
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current_bits = get_current_mdwe();
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