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| author | Marc Zyngier <Marc.Zyngier@arm.com> | 2013-06-21 12:06:55 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2013-06-24 15:26:41 +0100 |
| commit | b8e4a4740fa2b17c0a447b3ab783b3dc10702e27 (patch) | |
| tree | d6315409786d92102af8e057c8c4183d2d002101 /arch/arm/mm/context.c | |
| parent | ae120d9edfe96628f03d87634acda0bfa7110632 (diff) | |
| download | linux-b8e4a4740fa2b17c0a447b3ab783b3dc10702e27.tar.bz2 | |
ARM: 7768/1: prevent risks of out-of-bound access in ASID allocator
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.
Cc: <stable@vger.kernel.org> # 3.9
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>
Diffstat (limited to 'arch/arm/mm/context.c')
| -rw-r--r-- | arch/arm/mm/context.c | 17 |
1 files changed, 8 insertions, 9 deletions
diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c index 8e12fcbb2c63..83e09058f96f 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)); } |