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authorMarc Zyngier <Marc.Zyngier@arm.com>2013-06-21 12:06:55 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-07-21 18:21:34 -0700
commit4aa6022129a8b5e0b0e42815521071ce7a766a84 (patch)
tree19eb1705accf3dd1c59966efd7a0761270f330c8
parentb7dc4032cd44843ea93119adb00a5f15b7b05943 (diff)
downloadvexpress-lsk-4aa6022129a8b5e0b0e42815521071ce7a766a84.tar.gz
ARM: 7768/1: prevent risks of out-of-bound access in ASID allocator
commit b8e4a4740fa2b17c0a447b3ab783b3dc10702e27 upstream. On a CPU that never ran anything, both the active and reserved ASID fields are set to zero. In this case the ASID_TO_IDX() macro will return -1, which is not a very useful value to index a bitmap. Instead of trying to offset the ASID so that ASID #1 is actually bit 0 in the asid_map bitmap, just always ignore bit 0 and start the search from bit 1. This makes the code a bit more readable, and without risk of OoB access. Acked-by: Will Deacon <will.deacon@arm.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Reported-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--arch/arm/mm/context.c17
1 files changed, 8 insertions, 9 deletions
diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c
index 8e12fcbb2c6..83e09058f96 100644
--- a/arch/arm/mm/context.c
+++ b/arch/arm/mm/context.c
@@ -39,10 +39,7 @@
* non 64-bit operations.
*/
#define ASID_FIRST_VERSION (1ULL << ASID_BITS)
-#define NUM_USER_ASIDS (ASID_FIRST_VERSION - 1)
-
-#define ASID_TO_IDX(asid) ((asid & ~ASID_MASK) - 1)
-#define IDX_TO_ASID(idx) ((idx + 1) & ~ASID_MASK)
+#define NUM_USER_ASIDS ASID_FIRST_VERSION
static DEFINE_RAW_SPINLOCK(cpu_asid_lock);
static atomic64_t asid_generation = ATOMIC64_INIT(ASID_FIRST_VERSION);
@@ -137,7 +134,7 @@ static void flush_context(unsigned int cpu)
*/
if (asid == 0)
asid = per_cpu(reserved_asids, i);
- __set_bit(ASID_TO_IDX(asid), asid_map);
+ __set_bit(asid & ~ASID_MASK, asid_map);
}
per_cpu(reserved_asids, i) = asid;
}
@@ -176,17 +173,19 @@ static u64 new_context(struct mm_struct *mm, unsigned int cpu)
/*
* Allocate a free ASID. If we can't find one, take a
* note of the currently active ASIDs and mark the TLBs
- * as requiring flushes.
+ * as requiring flushes. We always count from ASID #1,
+ * as we reserve ASID #0 to switch via TTBR0 and indicate
+ * rollover events.
*/
- asid = find_first_zero_bit(asid_map, NUM_USER_ASIDS);
+ asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1);
if (asid == NUM_USER_ASIDS) {
generation = atomic64_add_return(ASID_FIRST_VERSION,
&asid_generation);
flush_context(cpu);
- asid = find_first_zero_bit(asid_map, NUM_USER_ASIDS);
+ asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1);
}
__set_bit(asid, asid_map);
- asid = generation | IDX_TO_ASID(asid);
+ asid |= generation;
cpumask_clear(mm_cpumask(mm));
}