There have been a couple of reports that the two sides of the
overlaps() calculation are redundant. I spent way too much time
looking at this, but I became convinced that they are redundant
when a little test program of mine produced identical disassembly
for both versions of the check.
Remove the second condition. It is exactly the same as the first.
Fixes: 91ee8f5c1f50 ("x86/mm/cpa: Allow range check for static protections")
Reported-by: David Binderman <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: [email protected]
---
arch/x86/mm/pat/set_memory.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index e9b448d1b1b70..fdc00516c0b54 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -435,8 +435,7 @@ static void cpa_flush(struct cpa_data *data, int cache)
static bool overlaps(unsigned long r1_start, unsigned long r1_end,
unsigned long r2_start, unsigned long r2_end)
{
- return (r1_start <= r2_end && r1_end >= r2_start) ||
- (r2_start <= r1_end && r2_end >= r1_start);
+ return (r1_start <= r2_end && r1_end >= r2_start);
}
#ifdef CONFIG_PCI_BIOS
--
2.34.1
On 1/23/2024 8:36 AM, Dave Hansen wrote:
> There have been a couple of reports that the two sides of the
> overlaps() calculation are redundant. I spent way too much time
> looking at this, but I became convinced that they are redundant
> when a little test program of mine produced identical disassembly
> for both versions of the check.
>
> Remove the second condition. It is exactly the same as the first.
>
> Fixes: 91ee8f5c1f50 ("x86/mm/cpa: Allow range check for static protections")
> Reported-by: David Binderman <[email protected]>
> Cc: Andy Lutomirski <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: [email protected]
> ---
> arch/x86/mm/pat/set_memory.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
Reviewed-by: Sohil Mehta <[email protected]>
> diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> index e9b448d1b1b70..fdc00516c0b54 100644
> --- a/arch/x86/mm/pat/set_memory.c
> +++ b/arch/x86/mm/pat/set_memory.c
> @@ -435,8 +435,7 @@ static void cpa_flush(struct cpa_data *data, int cache)
> static bool overlaps(unsigned long r1_start, unsigned long r1_end,
> unsigned long r2_start, unsigned long r2_end)
> {
> - return (r1_start <= r2_end && r1_end >= r2_start) ||
> - (r2_start <= r1_end && r2_end >= r1_start);
> + return (r1_start <= r2_end && r1_end >= r2_start);
> }
>
> #ifdef CONFIG_PCI_BIOS