redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

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>
hifive-unleashed-5.1
Marc Zyngier 2013-06-21 12:06:55 +01:00 committed by Russell King
parent ae120d9edf
commit b8e4a4740f
1 changed files with 8 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
arch/arm/mm/context.c
View File

@ -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));
}