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bh=mZPCbr0rDs8wcMO8G+Ur+xnvhS6uTOIeQkjfiLGhRhI=; b=iw7ggv/X3N05q2pfYNF1JFfKAjWUbQiHg8MOZ7T+C5FX8VrWhFOAwb8o jz3n7eUHrzBsPVE+EKX7NjgQuSzxA7tUyigCh7dfKEJtETXE0aWeakn1H ox44+1MOjbzeGOPl5UzzTMsLuJv59flgRkByl0gSwSir5gAQdQOrMnIu6 Z+RgOYYA5OOjeUlFXGCxDwNlxVDsbxYRr7ujnmRjsrXUNoH30rGw7MHR3 SVAZ+Gcx3M9fC9jFXYmzJbDcQGZ9LXLRWe4hw6C1/syWJeVZlLyXjPw2R AK1eb0/srWyTLr9LPBQWZRrpoSC+asBXS8GO01Y1otEqj562ymxVfk+gD A==; X-IronPort-AV: E=McAfee;i="6600,9927,11024"; a="6564381" X-IronPort-AV: E=Sophos;i="6.07,154,1708416000"; d="scan'208";a="6564381" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by orvoesa108.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2024 19:17:18 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.07,154,1708416000"; d="scan'208";a="20489917" Received: from rpwilson-mobl.amr.corp.intel.com (HELO rpedgeco-desk4.intel.com) ([10.251.11.187]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2024 19:17:18 -0700 From: Rick Edgecombe To: Liam.Howlett@oracle.com, akpm@linux-foundation.org, bp@alien8.de, broonie@kernel.org, christophe.leroy@csgroup.eu, dave.hansen@linux.intel.com, debug@rivosinc.com, hpa@zytor.com, keescook@chromium.org, kirill.shutemov@linux.intel.com, luto@kernel.org, mingo@redhat.com, peterz@infradead.org, tglx@linutronix.de, x86@kernel.org Cc: rick.p.edgecombe@intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v4 13/14] x86/mm: Care about shadow stack guard gap during placement Date: Mon, 25 Mar 2024 19:16:55 -0700 Message-Id: <20240326021656.202649-14-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240326021656.202649-1-rick.p.edgecombe@intel.com> References: <20240326021656.202649-1-rick.p.edgecombe@intel.com> MIME-Version: 1.0 X-Stat-Signature: hau6pcsx4go4cg59xzcjnfinbxagz513 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: A88CE18000F X-Rspam-User: X-HE-Tag: 1711419448-343328 X-HE-Meta: U2FsdGVkX1+Fb+On68cjL5J9nv2+lC5D2QJGX4C9UUMOMNofjXGDqcXkSy9s5N7UPlkw8jE7ENH+8FX9ozjTLyF6/DgXxyIAMwzEIhnp6psRaQV9mOJQ8/HL2W7enzrNPaTuZo98oNizZf3yntkhjt8j28Joz4FtDz8tzURskSH/Un4fc0NUquoLZ6IHmwdw2lzmq8pYNBUqOcd++A8wfsMIL1x6b/LvA3d6bUDPC7FvNERfW/FtIEt7R+lP+xohg1jGrIEDtBIUDCQG4RGFziX/60XLBTKCDGmsRZWwwGdW/VtBMuYGnFMrZbS8e0yPevgSTn5N1hwBs42QGr9TJc4ohiSCG3RqKTV4RbQYrF0yeKAR5+6NpktePlOTUT+SsgZ2Y7l/29nUzgOlIIklJs16quCy3xrZMUwpUhi1QfUQaRYLRdeXQbyxNjNw9wWxYPOycddSIfhgYBDVTSqceu36r6kRKykjdTG7Qnv40v6l+siXQoXooaq5Isv8YKTgro7mlrnrnEnyrlgOM99hG1ZEHXQWJ3PiG9fUVCiCpoz/8DIquSypC1P3D2XacV0jmEv+esSQqRU20qFPYs/CeM/Wi6Lyn9Og/rHwPf7ZyLMyqclAgAw0U/hp5k+KZkpIEJrkJaBC8ayOnWcJA/odgQPzIif3zlb4n2WXmLwy3KWK0HPCr7xhRJbspNdVI0kqx2BgZ+CMO8N+NVfgRWlZmq5bpbhiUun0j2XXfMSyTACUUodx/c5b1dLPcOqgxFdRnO4QjVgv8uHgp/F2b8IQ/cWR9NttkuCl7Rlajl71IoigPatNooSSr62SOE0FnAXay4DilPZxlauAER0UCPkif7uB6KAQXTTZ+AP8Fri9Gd2coERPNOTk8t2aRoM6TOg0MgnKHdH9ip9P4y9/V1480KqdC3RtwVpEMwZcYR3yV8TBOJkZCXZPFL/ybL7eHqnHEmzp45QdjGrM/do+OPk VQI95Gpi ADo+ASXKUDc7qEkue20s2p5pO6SluNM/DaaPQoHQFLuFrkDMYNdg3nzPTzLQGcBvoo7gIkHG7D2y7JmTpptZVAlel8sS4dmabnMVgQw1mBNNFinTHGCgXrOk5iQcxEGPFCAS/28abe3TYzdhS4cSocckGVrTxHHsGKWwZsoLqsK2+2VWXKIyRSwjRCOyJr8HtDzsB X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: When memory is being placed, mmap() will take care to respect the guard gaps of certain types of memory (VM_SHADOWSTACK, VM_GROWSUP and VM_GROWSDOWN). In order to ensure guard gaps between mappings, mmap() needs to consider two things: 1. That the new mapping isn’t placed in an any existing mappings guard gaps. 2. That the new mapping isn’t placed such that any existing mappings are not in *its* guard gaps. The long standing behavior of mmap() is to ensure 1, but not take any care around 2. So for example, if there is a PAGE_SIZE free area, and a mmap() with a PAGE_SIZE size, and a type that has a guard gap is being placed, mmap() may place the shadow stack in the PAGE_SIZE free area. Then the mapping that is supposed to have a guard gap will not have a gap to the adjacent VMA. Now that the vm_flags is passed into the arch get_unmapped_area()'s, and vm_unmapped_area() is ready to consider it, have VM_SHADOW_STACK's get guard gap consideration for scenario 2. Signed-off-by: Rick Edgecombe --- arch/x86/kernel/sys_x86_64.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c index 75966afb6251..01d7cd85ef97 100644 --- a/arch/x86/kernel/sys_x86_64.c +++ b/arch/x86/kernel/sys_x86_64.c @@ -112,6 +112,14 @@ static void find_start_end(unsigned long addr, unsigned long flags, *end = task_size_64bit(addr > DEFAULT_MAP_WINDOW); } +static inline unsigned long stack_guard_placement(vm_flags_t vm_flags) +{ + if (vm_flags & VM_SHADOW_STACK) + return PAGE_SIZE; + + return 0; +} + unsigned long arch_get_unmapped_area_vmflags(struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags, vm_flags_t vm_flags) @@ -141,6 +149,7 @@ arch_get_unmapped_area_vmflags(struct file *filp, unsigned long addr, unsigned l info.low_limit = begin; info.high_limit = end; info.align_offset = pgoff << PAGE_SHIFT; + info.start_gap = stack_guard_placement(vm_flags); if (filp) { info.align_mask = get_align_mask(); info.align_offset += get_align_bits(); @@ -190,6 +199,7 @@ arch_get_unmapped_area_topdown_vmflags(struct file *filp, unsigned long addr0, info.low_limit = PAGE_SIZE; info.high_limit = get_mmap_base(0); + info.start_gap = stack_guard_placement(vm_flags); /* * If hint address is above DEFAULT_MAP_WINDOW, look for unmapped area