From: Deepak Gupta <debug@rivosinc•com>
To: Mark Brown <broonie@kernel•org>
Cc: Richard Henderson <richard.henderson@linaro•org>,
Ivan Kokshaysky <ink@jurassic•park.msu.ru>,
Matt Turner <mattst88@gmail•com>,
Vineet Gupta <vgupta@kernel•org>,
Russell King <linux@armlinux•org.uk>, Guo Ren <guoren@kernel•org>,
Huacai Chen <chenhuacai@kernel•org>,
WANG Xuerui <kernel@xen0n•name>,
"James E.J. Bottomley" <James.Bottomley@hansenpartnership•com>,
Helge Deller <deller@gmx•de>,
Michael Ellerman <mpe@ellerman•id.au>,
Nicholas Piggin <npiggin@gmail•com>,
Christophe Leroy <christophe.leroy@csgroup•eu>,
Naveen N Rao <naveen@kernel•org>,
Alexander Gordeev <agordeev@linux•ibm.com>,
Gerald Schaefer <gerald.schaefer@linux•ibm.com>,
Heiko Carstens <hca@linux•ibm.com>,
Vasily Gorbik <gor@linux•ibm.com>,
Christian Borntraeger <borntraeger@linux•ibm.com>,
Sven Schnelle <svens@linux•ibm.com>,
Yoshinori Sato <ysato@users•sourceforge.jp>,
Rich Felker <dalias@libc•org>,
John Paul Adrian Glaubitz <glaubitz@physik•fu-berlin.de>,
"David S. Miller" <davem@davemloft•net>,
Andreas Larsson <andreas@gaisler•com>,
Thomas Gleixner <tglx@linutronix•de>,
Ingo Molnar <mingo@redhat•com>, Borislav Petkov <bp@alien8•de>,
Dave Hansen <dave.hansen@linux•intel.com>,
x86@kernel•org, "H. Peter Anvin" <hpa@zytor•com>,
Chris Zankel <chris@zankel•net>,
Max Filippov <jcmvbkbc@gmail•com>,
Andrew Morton <akpm@linux-foundation•org>,
"Liam R. Howlett" <Liam.Howlett@oracle•com>,
Vlastimil Babka <vbabka@suse•cz>,
Lorenzo Stoakes <lorenzo.stoakes@oracle•com>,
Catalin Marinas <catalin.marinas@arm•com>,
Will Deacon <will@kernel•org>,
linux-arm-kernel@lists•infradead.org,
linux-alpha@vger•kernel.org, linux-kernel@vger•kernel.org,
linux-snps-arc@lists•infradead.org, linux-csky@vger•kernel.org,
loongarch@lists•linux.dev, linux-parisc@vger•kernel.org,
linuxppc-dev@lists•ozlabs.org, linux-s390@vger•kernel.org,
linux-sh@vger•kernel.org, sparclinux@vger•kernel.org,
linux-mm@kvack•org, Rick Edgecombe <rick.p.edgecombe@intel•com>
Subject: Re: [PATCH 3/3] mm: Care about shadow stack guard gap when getting an unmapped area
Date: Wed, 4 Sep 2024 11:51:53 -0700 [thread overview]
Message-ID: <ZtisSerxbnDaWr5l@debug.ba.rivosinc.com> (raw)
In-Reply-To: <20240902-mm-generic-shadow-stack-guard-v1-3-9acda38b3dd3@kernel.org>
On Mon, Sep 02, 2024 at 08:08:15PM +0100, Mark Brown wrote:
>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.
>
>Architectures which do not have this feature will define VM_SHADOW_STACK
>to VM_NONE and hence be unaffected.
>
>Suggested-by: Rick Edgecombe <rick.p.edgecombe@intel•com>
>Signed-off-by: Mark Brown <broonie@kernel•org>
>---
> mm/mmap.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
>diff --git a/mm/mmap.c b/mm/mmap.c
>index b06ba847c96e..902c482b6084 100644
>--- a/mm/mmap.c
>+++ b/mm/mmap.c
>@@ -1753,6 +1753,14 @@ static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
> return gap;
> }
>
>+static inline unsigned long stack_guard_placement(vm_flags_t vm_flags)
>+{
>+ if (vm_flags & VM_SHADOW_STACK)
>+ return PAGE_SIZE;
>+
>+ return 0;
>+}
>+
> /*
> * Search for an unmapped address range.
> *
>@@ -1814,6 +1822,7 @@ generic_get_unmapped_area(struct file *filp, unsigned long addr,
> info.length = len;
> info.low_limit = mm->mmap_base;
> info.high_limit = mmap_end;
>+ info.start_gap = stack_guard_placement(vm_flags);
> return vm_unmapped_area(&info);
> }
>
>@@ -1863,6 +1872,7 @@ generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
> info.length = len;
> info.low_limit = PAGE_SIZE;
> info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);
>+ info.start_gap = stack_guard_placement(vm_flags);
> addr = vm_unmapped_area(&info);
>
> /*
>
lgtm
Reviewed-by: Deepak Gupta <debug@rivosinc•com>
>--
>2.39.2
>
prev parent reply other threads:[~2024-09-04 22:33 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-02 19:08 [PATCH 0/3] mm: Care about shadow stack guard gap when getting an unmapped area Mark Brown
2024-09-02 19:08 ` [PATCH 1/3] mm: Make arch_get_unmapped_area() take vm_flags by default Mark Brown
2024-09-03 17:43 ` Lorenzo Stoakes
2024-09-03 19:35 ` Liam R. Howlett
2024-09-03 19:50 ` Helge Deller
2024-09-02 19:08 ` [PATCH 2/3] mm: Pass vm_flags to generic_get_unmapped_area() Mark Brown
2024-09-03 17:44 ` Lorenzo Stoakes
2024-09-03 19:37 ` Liam R. Howlett
2024-09-04 4:13 ` Michael Ellerman
2024-09-04 18:53 ` Deepak Gupta
2024-09-02 19:08 ` [PATCH 3/3] mm: Care about shadow stack guard gap when getting an unmapped area Mark Brown
2024-09-03 17:49 ` Lorenzo Stoakes
2024-09-03 18:20 ` Mark Brown
2024-09-03 19:24 ` Lorenzo Stoakes
2024-09-03 19:41 ` Liam R. Howlett
2024-09-03 19:57 ` Mark Brown
2024-09-04 19:07 ` Deepak Gupta
2024-09-04 18:51 ` Deepak Gupta [this message]
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