From: Catalin Marinas <catalin.marinas@arm.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Josef Bacik <josef@toxicpanda.com>,
David Sterba <dsterba@suse.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Will Deacon <will@kernel.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-btrfs@vger.kernel.org
Subject: [PATCH 2/3] arm64: Add support for sub-page faults user probing
Date: Wed, 24 Nov 2021 19:20:23 +0000 [thread overview]
Message-ID: <20211124192024.2408218-3-catalin.marinas@arm.com> (raw)
In-Reply-To: <20211124192024.2408218-1-catalin.marinas@arm.com>
With MTE, even if the pte allows an access, a mismatched tag somewhere
within a page can still cause a fault. Select ARCH_HAS_SUBPAGE_FAULTS if
MTE is enabled and implement probe_user_writeable().
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/uaccess.h | 33 ++++++++++++++++++++++++++++++++
2 files changed, 34 insertions(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index c4207cf9bb17..dff89fd0d817 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1777,6 +1777,7 @@ config ARM64_MTE
depends on AS_HAS_LSE_ATOMICS
# Required for tag checking in the uaccess routines
depends on ARM64_PAN
+ select ARCH_HAS_SUBPAGE_FAULTS
select ARCH_USES_HIGH_VMA_FLAGS
help
Memory Tagging (part of the ARMv8.5 Extensions) provides
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 6e2e0b7031ab..4bf947e9f9bf 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -445,4 +445,37 @@ static inline int __copy_from_user_flushcache(void *dst, const void __user *src,
}
#endif
+#ifdef CONFIG_ARCH_HAS_SUBPAGE_FAULTS
+static inline size_t __mte_probe_user_range(const char __user *uaddr,
+ size_t size)
+{
+ const char __user *end = uaddr + size;
+ int err = 0;
+ char val;
+
+ uaddr = PTR_ALIGN_DOWN(uaddr, MTE_GRANULE_SIZE);
+ while (uaddr < end) {
+ /*
+ * A read is sufficient for MTE, the caller should have probed
+ * for the pte write permission.
+ */
+ __raw_get_user(val, uaddr, err);
+ if (err)
+ return end - uaddr;
+ uaddr += MTE_GRANULE_SIZE;
+ }
+ (void)val;
+
+ return 0;
+}
+
+static inline size_t probe_user_writable(const void __user *uaddr,
+ size_t size)
+{
+ if (!system_supports_mte())
+ return 0;
+ return __mte_probe_user_range(uaddr, size);
+}
+#endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */
+
#endif /* __ASM_UACCESS_H */
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next prev parent reply other threads:[~2021-11-24 19:22 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-24 19:20 [PATCH 0/3] Avoid live-lock in fault-in+uaccess loops with sub-page faults Catalin Marinas
2021-11-24 19:20 ` [PATCH 1/3] mm: Introduce fault_in_exact_writeable() to probe for " Catalin Marinas
2021-11-24 19:20 ` Catalin Marinas [this message]
2021-11-24 19:20 ` [PATCH 3/3] btrfs: Avoid live-lock in search_ioctl() on hardware with " Catalin Marinas
2021-11-24 20:03 ` Matthew Wilcox
2021-11-24 20:37 ` Catalin Marinas
2021-11-25 22:25 ` Andreas Gruenbacher
2021-11-25 22:42 ` Catalin Marinas
2021-11-26 22:29 ` Andreas Gruenbacher
2021-11-26 22:57 ` Catalin Marinas
2021-11-27 3:52 ` Andreas Gruenbacher
2021-11-27 14:33 ` Catalin Marinas
2021-11-27 12:39 ` Andreas Gruenbacher
2021-11-27 15:21 ` Catalin Marinas
2021-11-27 18:05 ` Andreas Gruenbacher
2021-11-29 12:16 ` Catalin Marinas
2021-11-29 13:33 ` Andreas Gruenbacher
2021-11-29 15:36 ` Catalin Marinas
2021-11-29 18:40 ` Linus Torvalds
2021-11-29 19:31 ` Andreas Gruenbacher
2021-11-29 20:56 ` Catalin Marinas
2021-11-29 21:53 ` Linus Torvalds
2021-11-29 23:12 ` Catalin Marinas
2021-11-29 13:52 ` Catalin Marinas
2021-11-24 23:00 ` Linus Torvalds
2021-11-25 11:10 ` Catalin Marinas
2021-11-25 18:13 ` Linus Torvalds
2021-11-25 20:43 ` Catalin Marinas
2021-11-25 21:02 ` Matthew Wilcox
2021-11-25 21:29 ` Catalin Marinas
2021-11-25 21:40 ` Andreas Gruenbacher
2021-11-26 16:42 ` David Sterba
2021-11-24 21:36 ` [PATCH 0/3] Avoid live-lock in fault-in+uaccess loops " Andrew Morton
2021-11-24 22:31 ` Catalin Marinas
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