From 25d4054cc97484f2555709ac233f955f674e026a Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Wed, 4 Sep 2024 17:57:59 +0100 Subject: mm: make arch_get_unmapped_area() take vm_flags by default Patch series "mm: Care about shadow stack guard gap when getting an unmapped area", v2. As covered in the commit log for c44357c2e76b ("x86/mm: care about shadow stack guard gap during placement") our current mmap() implementation does not take care to ensure that a new mapping isn't placed with existing mappings inside it's own guard gaps. This is particularly important for shadow stacks since if two shadow stacks end up getting placed adjacent to each other then they can overflow into each other which weakens the protection offered by the feature. On x86 there is a custom arch_get_unmapped_area() which was updated by the above commit to cover this case by specifying a start_gap for allocations with VM_SHADOW_STACK. Both arm64 and RISC-V have equivalent features and use the generic implementation of arch_get_unmapped_area() so let's make the equivalent change there so they also don't get shadow stack pages placed without guard pages. The arm64 and RISC-V shadow stack implementations are currently on the list: https://lore.kernel.org/r/20240829-arm64-gcs-v12-0-42fec94743 https://lore.kernel.org/lkml/20240403234054.2020347-1-debug@rivosinc.com/ Given the addition of the use of vm_flags in the generic implementation we also simplify the set of possibilities that have to be dealt with in the core code by making arch_get_unmapped_area() take vm_flags as standard. This is a bit invasive since the prototype change touches quite a few architectures but since the parameter is ignored the change is straightforward, the simplification for the generic code seems worth it. This patch (of 3): When we introduced arch_get_unmapped_area_vmflags() in 961148704acd ("mm: introduce arch_get_unmapped_area_vmflags()") we did so as part of properly supporting guard pages for shadow stacks on x86_64, which uses a custom arch_get_unmapped_area(). Equivalent features are also present on both arm64 and RISC-V, both of which use the generic implementation of arch_get_unmapped_area() and will require equivalent modification there. Rather than continue to deal with having two versions of the functions let's bite the bullet and have all implementations of arch_get_unmapped_area() take vm_flags as a parameter. The new parameter is currently ignored by all implementations other than x86. The only caller that doesn't have a vm_flags available is mm_get_unmapped_area(), as for the x86 implementation and the wrapper used on other architectures this is modified to supply no flags. No functional changes. Link: https://lkml.kernel.org/r/20240904-mm-generic-shadow-stack-guard-v2-0-a46b8b6dc0ed@kernel.org Link: https://lkml.kernel.org/r/20240904-mm-generic-shadow-stack-guard-v2-1-a46b8b6dc0ed@kernel.org Signed-off-by: Mark Brown Acked-by: Lorenzo Stoakes Reviewed-by: Liam R. Howlett Acked-by: Helge Deller [parisc] Cc: Alexander Gordeev Cc: Andreas Larsson Cc: Borislav Petkov Cc: Christian Borntraeger Cc: Christophe Leroy Cc: Chris Zankel Cc: Dave Hansen Cc: David S. Miller Cc: "Edgecombe, Rick P" Cc: Gerald Schaefer Cc: Guo Ren Cc: Heiko Carstens Cc: "H. Peter Anvin" Cc: Huacai Chen Cc: Ingo Molnar Cc: Ivan Kokshaysky Cc: James Bottomley Cc: John Paul Adrian Glaubitz Cc: Matt Turner Cc: Max Filippov Cc: Michael Ellerman Cc: Naveen N Rao Cc: Nicholas Piggin Cc: Richard Henderson Cc: Rich Felker Cc: Russell King Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: Thomas Gleixner Cc: Vasily Gorbik Cc: Vineet Gupta Cc: Vlastimil Babka Cc: WANG Xuerui Cc: Yoshinori Sato Signed-off-by: Andrew Morton --- arch/parisc/kernel/sys_parisc.c | 5 +++-- arch/parisc/mm/hugetlbpage.c | 2 +- 2 files changed, 4 insertions(+), 3 deletions(-) (limited to 'arch/parisc') diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.c index f7722451276e..f852fe274abe 100644 --- a/arch/parisc/kernel/sys_parisc.c +++ b/arch/parisc/kernel/sys_parisc.c @@ -167,7 +167,8 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp, } unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, - unsigned long len, unsigned long pgoff, unsigned long flags) + unsigned long len, unsigned long pgoff, unsigned long flags, + vm_flags_t vm_flags) { return arch_get_unmapped_area_common(filp, addr, len, pgoff, flags, UP); @@ -175,7 +176,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsigned long arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, - unsigned long flags) + unsigned long flags, vm_flags_t vm_flags) { return arch_get_unmapped_area_common(filp, addr, len, pgoff, flags, DOWN); diff --git a/arch/parisc/mm/hugetlbpage.c b/arch/parisc/mm/hugetlbpage.c index 0356199bd9e7..aa664f7ddb63 100644 --- a/arch/parisc/mm/hugetlbpage.c +++ b/arch/parisc/mm/hugetlbpage.c @@ -40,7 +40,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr, addr = ALIGN(addr, huge_page_size(h)); /* we need to make sure the colouring is OK */ - return arch_get_unmapped_area(file, addr, len, pgoff, flags); + return arch_get_unmapped_area(file, addr, len, pgoff, flags, 0); } -- cgit v1.2.3