From c4f1b56f3f78d22d8f73bd9264a7c2e6d74432ff Mon Sep 17 00:00:00 2001 From: Lorenzo Stoakes Date: Thu, 2 Jan 2025 12:10:51 +0000 Subject: [PATCH] mips: vdso: prefer do_mmap() to mmap_region() Patch series "mm: update mips to use do_mmap(), make mmap_region() internal". Currently the only user of mmap_region() outside of the memory management code is the MIPS VDSO implementation. This uses mmap_region() to map a 'delay slot emulation page' at the top of the stack which is read-only and executable. This mapping requires that an already-acquired mmap write lock is utilised and that uffd and populate logic is ignored. This rules out vm_mmap(), however do_mmap() fits the bill. Adapt this code to use do_mmap() and then once done, make mmap_region() internal and userland testable, and avoid any other uses of mmap_region(), which is absolutely and strictly an internal mm function which bypasses a great number of checks and logic. This patch (of 2): mmap_region() is an internal memory management implementation detail that is not intended to be used outside of the memory management subsystem. Map the delay slot emulation page using do_mmap() which makes use of the already-held mmap write lock and bypasses unneeded populate and userfaultfd logic. This should have the precise same behaviour as the existing logic. Link: https://lkml.kernel.org/r/cover.1735819274.git.lorenzo.stoakes@oracle.com Link: https://lkml.kernel.org/r/ef076e381570f709e5c2c142dc030ec5b3309a0e.1735819274.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Liam R. Howlett Cc: Jann Horn Cc: Thomas Bogendoerfer Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- arch/mips/kernel/vdso.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c index 4c8e3c0aa2104..75c9d3618f588 100644 --- a/arch/mips/kernel/vdso.c +++ b/arch/mips/kernel/vdso.c @@ -11,6 +11,7 @@ #include #include #include +#include #include #include #include @@ -97,11 +98,12 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) return -EINTR; if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) { + unsigned long unused; + /* Map delay slot emulation page */ - base = mmap_region(NULL, STACK_TOP, PAGE_SIZE, - VM_READ | VM_EXEC | - VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC, - 0, NULL); + base = do_mmap(NULL, STACK_TOP, PAGE_SIZE, PROT_READ | PROT_EXEC, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, 0, 0, &unused, + NULL); if (IS_ERR_VALUE(base)) { ret = base; goto out; -- 2.49.0