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

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: 17dbca119312 ("x86/speculation/l1tf: Add sysfs reporting for l1tf")
Fixes: 377eeaa8e11f ("x86/speculation/l1tf: Limit swap file size to MAX_PA/2")
Reported-by: Dominique Leuenberger <[email protected]>
Reported-by: Adrian Schroeter <[email protected]>
Signed-off-by: Vlastimil Babka <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Andi Kleen <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: "H . Peter Anvin" <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 682286aca88141c5ec5315597020f6e7e0c9b0fc..a0a52274cb4a2e377ac71affc00039da527bd0c6 100644 (file)
--- 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
index acfab322fbe062c24dee168f6b79e25e38290c68..02de3d6065c40693112646ef372ffd8887e7a6da 100644 (file)
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -923,7 +923,7 @@ 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.
@@ -931,7 +931,7 @@ unsigned long max_swapfile_size(void)
 #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;
 }