Re: [PATCH v2 4/6] powerpc/pkeys: Preallocate execute-only key
flat view
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2018-06-19 12:40:15
Ram Pai [off-list ref] writes:
execute-only key is allocated dynamically. This is a problem. When a thread implicitly creates a execute-only key, and resets UAMOR for that key, the UAMOR value does not percolate to all the other threads. Any other thread may ignorantly change the permissions on the key. This can cause the key to be not execute-only for that thread. Preallocate the execute-only key and ensure that no thread can change the permission of the key, by resetting the corresponding bit in UAMOR.
OK this is a non-ABI changing bug fix AFAICS.
I'll add:
Fixes: 5586cf61e108 ("powerpc: introduce execute-only pkey")
Cc: stable@vger.kernel.org # v4.16+
quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c index b681bec..1f2389f 100644 --- a/arch/powerpc/mm/pkeys.c +++ b/arch/powerpc/mm/pkeys.c@@ -25,6 +25,7 @@ #define IAMR_EX_BIT 0x1UL #define PKEY_REG_BITS (sizeof(u64)*8) #define pkeyshift(pkey) (PKEY_REG_BITS - ((pkey+1) * AMR_BITS_PER_PKEY)) +#define EXECUTE_ONLY_KEY 2
Do we ensure we have at least 3 keys anywhere? cheers