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authorVlastimil Babka <vbabka@suse.cz>2018-08-23 15:44:18 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-09-05 09:18:38 +0200
commit7b69cd6fa088e473869512672969e6c490cac1b6 (patch)
tree2244805ad7ed356820ed874399e1a2ef19245fa3
parent6a56bd7f2ea31d4c86849b8f67d4e2dc1cb5b788 (diff)
x86/speculation/l1tf: Fix off-by-one error when warning that system has too much RAM
commit b0a182f875689647b014bc01d36b340217792852 upstream. Two users have reported [1] that they have an "extremely unlikely" system with more than MAX_PA/2 memory and L1TF mitigation is not effective. In fact it's a CPU with 36bits phys limit (64GB) and 32GB memory, but due to holes in the e820 map, the main region is almost 500MB over the 32GB limit: [ 0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000081effffff] usable Suggestions to use 'mem=32G' to enable the L1TF mitigation while losing the 500MB revealed, that there's an off-by-one error in the check in l1tf_select_mitigation(). l1tf_pfn_limit() returns the last usable pfn (inclusive) and the range check in the mitigation path does not take this into account. Instead of amending the range check, make l1tf_pfn_limit() return the first PFN which is over the limit which is less error prone. Adjust the other users accordingly. [1] https://bugzilla.suse.com/show_bug.cgi?id=1105536 Fixes: 17dbca119312 ("x86/speculation/l1tf: Add sysfs reporting for l1tf") Reported-by: George Anchev <studio@anchev.net> Reported-by: Christopher Snowhill <kode54@gmail.com> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: "H . Peter Anvin" <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andi Kleen <ak@linux.intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180823134418.17008-1-vbabka@suse.cz Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/x86/include/asm/processor.h2
-rw-r--r--arch/x86/mm/init.c2
-rw-r--r--arch/x86/mm/mmap.c2
3 files changed, 3 insertions, 3 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index b023f127eee3..337c52192278 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -174,7 +174,7 @@ extern void cpu_detect(struct cpuinfo_x86 *c);
static inline unsigned long long l1tf_pfn_limit(void)
{
- return BIT_ULL(boot_cpu_data.x86_phys_bits - 1 - PAGE_SHIFT) - 1;
+ return BIT_ULL(boot_cpu_data.x86_phys_bits - 1 - PAGE_SHIFT);
}
extern void early_cpu_init(void);
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 3bf0ff0d784a..f00eb52c16a6 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -779,7 +779,7 @@ 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 long l1tf_limit = l1tf_pfn_limit() + 1;
+ unsigned long long l1tf_limit = l1tf_pfn_limit();
/*
* We encode swap offsets also with 3 bits below those for pfn
* which makes the usable limit higher.
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 9a055ea279eb..528d71b50c3b 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -138,7 +138,7 @@ bool pfn_modify_allowed(unsigned long pfn, pgprot_t prot)
/* If it's real memory always allow */
if (pfn_valid(pfn))
return true;
- if (pfn > l1tf_pfn_limit() && !capable(CAP_SYS_ADMIN))
+ if (pfn >= l1tf_pfn_limit() && !capable(CAP_SYS_ADMIN))
return false;
return true;
}