@@ -479,4 +479,37 @@ static inline int __copy_from_user_flush
}
#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 */
@@ -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
The patch titled Subject: arm64: add support for sub-page faults user probing has been removed from the -mm tree. Its filename was arm64-add-support-for-sub-page-faults-user-probing.patch This patch was dropped because an updated version will be merged ------------------------------------------------------ From: Catalin Marinas <catalin.marinas@arm.com> Subject: arm64: add support for sub-page faults user probing 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(). Link: https://lkml.kernel.org/r/20211124192024.2408218-3-catalin.marinas@arm.com Fixes: a48b73eca4ce ("btrfs: fix potential deadlock in the search ioctl") Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Gruenbacher <agruenba@redhat.com> Cc: David Sterba <dsterba@suse.com> Cc: Josef Bacik <josef@toxicpanda.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Will Deacon <will@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- arch/arm64/Kconfig | 1 arch/arm64/include/asm/uaccess.h | 33 +++++++++++++++++++++++++++++ 2 files changed, 34 insertions(+)