x86/speculation/l1tf: Fix overflow in l1tf_pfn_limit() on 32bit

tehcaster · KAGA-KOKO · commit 9df9516940a6 · 2018-08-20T18:04:42.000+02:00
On 32bit PAE kernels on 64bit hardware with enough physical bits, l1tf_pfn_limit() will overflow unsigned long. This in turn affects max_swapfile_size() and can lead to swapon returning -EINVAL. This has been observed in a 32bit guest with 42 bits physical address size, where max_swapfile_size() overflows exactly to 1 << 32, thus zero, and produces the following warning to dmesg: [ 6.396845] Truncating oversized swap area, only using 0k out of 2047996k Fix this by using unsigned long long instead. Fixes: 17dbca1 ("x86/speculation/l1tf: Add sysfs reporting for l1tf") Fixes: 377eeaa ("x86/speculation/l1tf: Limit swap file size to MAX_PA/2") Reported-by: Dominique Leuenberger <dimstar@suse.de> Reported-by: Adrian Schroeter <adrian@suse.de> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Andi Kleen <ak@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: "H . Peter Anvin" <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180820095835.5298-1-vbabka@suse.cz
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
@@ -181,9 +181,9 @@ extern const struct seq_operations cpuinfo_op;
 
 extern void cpu_detect(struct cpuinfo_x86 *c);
 
-static inline unsigned long l1tf_pfn_limit(void)
+static inline unsigned long long l1tf_pfn_limit(void)
 {
-	return BIT(boot_cpu_data.x86_phys_bits - 1 - PAGE_SHIFT) - 1;
+	return BIT_ULL(boot_cpu_data.x86_phys_bits - 1 - PAGE_SHIFT) - 1;
 }
 
 extern void early_cpu_init(void);
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
@@ -923,15 +923,15 @@ unsigned long max_swapfile_size(void)
 
 	if (boot_cpu_has_bug(X86_BUG_L1TF)) {
 		/* Limit the swap file size to MAX_PA/2 for L1TF workaround */
-		unsigned long l1tf_limit = l1tf_pfn_limit() + 1;
+		unsigned long long l1tf_limit = l1tf_pfn_limit() + 1;
 		/*
 		 * We encode swap offsets also with 3 bits below those for pfn
 		 * which makes the usable limit higher.
 		 */
 #if CONFIG_PGTABLE_LEVELS > 2
 		l1tf_limit <<= PAGE_SHIFT - SWP_OFFSET_FIRST_BIT;
 #endif
-		pages = min_t(unsigned long, l1tf_limit, pages);
+		pages = min_t(unsigned long long, l1tf_limit, pages);
 	}
 	return pages;
 }

Original file line number	Diff line number	Diff line change
`@@ -181,9 +181,9 @@ extern const struct seq_operations cpuinfo_op;`
`181`	`181`
`182`	`182`	`extern void cpu_detect(struct cpuinfo_x86 *c);`
`183`	`183`
`184`		`-static inline unsigned long l1tf_pfn_limit(void)`
	`184`	`+static inline unsigned long long l1tf_pfn_limit(void)`
`185`	`185`	`{`
`186`		`- return BIT(boot_cpu_data.x86_phys_bits - 1 - PAGE_SHIFT) - 1;`
	`186`	`+ return BIT_ULL(boot_cpu_data.x86_phys_bits - 1 - PAGE_SHIFT) - 1;`
`187`	`187`	`}`
`188`	`188`
`189`	`189`	`extern void early_cpu_init(void);`