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Subject[PATCH 4.18 051/123] x86/speculation/l1tf: Fix overflow in l1tf_pfn_limit() on 32bit
Date
4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vlastimil Babka <vbabka@suse.cz>

commit 9df9516940a61d29aedf4d91b483ca6597e7d480 upstream.

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 <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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/include/asm/processor.h | 4 ++--
arch/x86/mm/init.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)

--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -181,9 +181,9 @@ extern const struct seq_operations cpuin

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);
--- 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;
}

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