From d5aad4c2ca057e760a92a9a7d65bd38d72963f27 Mon Sep 17 00:00:00 2001 From: Zev Weiss Date: Mon, 26 Feb 2024 17:35:41 -0800 Subject: 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 793838138c15, "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 Acked-by: Helge Deller [parisc] Cc: Borislav Petkov Cc: David Hildenbrand Cc: Florent Revest Cc: "James E.J. Bottomley" Cc: Josh Triplett Cc: Kees Cook Cc: Miguel Ojeda Cc: Mike Rapoport (IBM) Cc: Oleg Nesterov Cc: Ondrej Mosnacek Cc: Rick Edgecombe Cc: Russell King (Oracle) Cc: Sam James Cc: Stefan Roesch Cc: Yang Shi Cc: Yin Fengwei Cc: [6.3+] Signed-off-by: Andrew Morton --- include/linux/mman.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'include') diff --git a/include/linux/mman.h b/include/linux/mman.h index dc7048824be8..bcb201ab7a41 100644 --- a/include/linux/mman.h +++ b/include/linux/mman.h @@ -162,6 +162,14 @@ calc_vm_flag_bits(unsigned long flags) unsigned long vm_commit_limit(void); +#ifndef arch_memory_deny_write_exec_supported +static inline bool arch_memory_deny_write_exec_supported(void) +{ + return true; +} +#define arch_memory_deny_write_exec_supported arch_memory_deny_write_exec_supported +#endif + /* * Denies creating a writable executable mapping or gaining executable permissions. * -- cgit v1.2.3