diff options
| author | Vlastimil Babka <vbabka@suse.cz> | 2018-08-23 15:44:18 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-09-05 09:20:07 +0200 |
| commit | f8d42d5c02084c936f0a7830e011b4395f30f06e (patch) | |
| tree | 0b6992d90db6010f08e73eb6defc239ad288f9ea /arch | |
| parent | fe0f40491bba65d904edd0147184bd9882cb7b7f (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>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/processor.h | 2 | ||||
| -rw-r--r-- | arch/x86/mm/init.c | 2 | ||||
| -rw-r--r-- | arch/x86/mm/mmap.c | 2 |
3 files changed, 3 insertions, 3 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index c3d53afef073..8d9ea8a4f229 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -175,7 +175,7 @@ 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 8c51000e3e61..90801a8f19c9 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -792,7 +792,7 @@ 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 5aad869fa205..74609a957c49 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; } |