Messages in this thread | | | Date | Mon, 27 Nov 2023 11:37:28 +0100 | Subject | Re: [PATCH v2] riscv: fix incorrect use of __user pointer | From | Clément Léger <> |
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On 27/11/2023 11:35, David Laight wrote: > From: Clément Léger >> Sent: 27 November 2023 10:24 >> >> On 25/11/2023 16:37, David Laight wrote: >>> ... >>>> @@ -491,7 +486,7 @@ int handle_misaligned_load(struct pt_regs *regs) >>>> >>>> val.data_u64 = 0; >>>> for (i = 0; i < len; i++) { >>>> - if (load_u8(regs, (void *)(addr + i), &val.data_bytes[i])) >>>> + if (load_u8(regs, addr + i, &val.data_bytes[i])) >>>> return -1; >>>> } >>> >>> I'd really have thought that you'd want to pull the kernel/user >>> check way outside the loop? >> >> Hi David, >> >> I hope the compiler is able to extract that 'if' out of the loop since >> regs isn't modified in the loop. Nevertheless, that could be more >> "clear" if put outside indeed. > > If has access regs->xxx then the compiler can't do so because it > will must assume that the assignment might alias into 'regs'. > That is even true for byte writes if 'strict-aliasing' is enabled > - which it isn't for linux kernel builds. > > It might do so if 'regs' were 'const'; it tends to assume that if > it can't change something nothing can - although that isn't true.
Ok, good to know ! As I said, I'll modify that in a subsequent patch.
Thanks,
Clément
> > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales)
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