Hi, Where is patch 1 of this series? It doesn't seem to have been Cc'd to linux-arm-kernel. Therefore, this can't be reviewed. Thanks. On Wed, Feb 07, 2024 at 05:26:18PM -0800, Zev Weiss wrote: > Hello, > > 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. > > (Note that I'm not an expert in either ARM arch details or the mm > subsystem, so please bear with me if I've botched something in the > above analysis.) > > 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. > > Since this was effectively a userspace-breaking change in v6.3 (with > newer MDWE-aware userspace on older pre-MDWE kernels the prctl would > simply fail safely) I've CCed -stable for v6.3+, though since the > patches depend on the PARISC one above it will only apply cleanly on > the linux-6.6.y and linux-6.7.y branches, since at least at time of > writing the 6.3 through 6.5 branches don't have that patch backported > (due to further missing dependencies [0]). > > > Thanks, > Zev > > [0] https://lore.kernel.org/all/2023112456-linked-nape-bf19@gregkh/ > > Zev Weiss (2): > prctl: Generalize PR_SET_MDWE support check to be per-arch > ARM: prctl: Reject PR_SET_MDWE on pre-ARMv6 > > arch/arm/include/asm/mman.h | 14 ++++++++++++++ > arch/parisc/include/asm/mman.h | 14 ++++++++++++++ > include/linux/mman.h | 8 ++++++++ > kernel/sys.c | 7 +++++-- > 4 files changed, 41 insertions(+), 2 deletions(-) > create mode 100644 arch/arm/include/asm/mman.h > create mode 100644 arch/parisc/include/asm/mman.h > > -- > 2.43.0 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
