Re: [PATCH 08/23] powerpc: Fix fallocate and fadvise64_64 compat parameter combination

["Nicholas Piggin" <npiggin@gmail.com>]

On Fri Sep 16, 2022 at 3:32 PM AEST, Rohan McLure wrote:
> As reported[1] by Arnd, the arch-specific fadvise64_64 and fallocate
> compatibility handlers assume parameters are passed with 32-bit
> big-endian ABI. This affects the assignment of odd-even parameter pairs
> to the high or low words of a 64-bit syscall parameter.
>
> Fix fadvise64_64 fallocate compat handlers to correctly swap upper/lower
> 32 bits conditioned on endianness.
>
> A future patch will replace the arch-specific compat fallocate with an
> asm-generic implementation. This patch is intended for ease of
> back-port.
>
> [1]: https://lore.kernel.org/all/be29926f-226e-48dc-871a-e29a54e80583@www.fastmail.com/
>
> Fixes: 57f48b4b74e7 ("powerpc/compat_sys: swap hi/lo parts of 64-bit syscall args in LE mode")
> Reported-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>

I'm still not sure if ppc32 is usable with LE kernel, but in any case
the patch is good I think.

Reviewed-by: Nicholas Piggin <npiggin@gmai.com>

> ---
> V4 -> V5: New patch.
> ---
>  arch/powerpc/include/asm/syscalls.h | 12 ++++++++++++
>  arch/powerpc/kernel/sys_ppc32.c     | 14 +-------------
>  arch/powerpc/kernel/syscalls.c      |  4 ++--
>  3 files changed, 15 insertions(+), 15 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
> index 21c2faaa2957..16b668515d15 100644
> --- a/arch/powerpc/include/asm/syscalls.h
> +++ b/arch/powerpc/include/asm/syscalls.h
> @@ -8,6 +8,18 @@
>  #include <linux/types.h>
>  #include <linux/compat.h>
>  
> +/*
> + * long long munging:
> + * The 32 bit ABI passes long longs in an odd even register pair.
> + * High and low parts are swapped depending on endian mode,
> + * so define a macro (similar to mips linux32) to handle that.
> + */
> +#ifdef __LITTLE_ENDIAN__
> +#define merge_64(low, high) ((u64)high << 32) | low
> +#else
> +#define merge_64(high, low) ((u64)high << 32) | low
> +#endif
> +
>  struct rtas_args;
>  
>  long sys_mmap(unsigned long addr, size_t len,
> diff --git a/arch/powerpc/kernel/sys_ppc32.c b/arch/powerpc/kernel/sys_ppc32.c
> index f4edcc9489fb..ba363328da2b 100644
> --- a/arch/powerpc/kernel/sys_ppc32.c
> +++ b/arch/powerpc/kernel/sys_ppc32.c
> @@ -56,18 +56,6 @@ unsigned long compat_sys_mmap2(unsigned long addr, size_t len,
>  	return sys_mmap(addr, len, prot, flags, fd, pgoff << 12);
>  }
>  
> -/* 
> - * long long munging:
> - * The 32 bit ABI passes long longs in an odd even register pair.
> - * High and low parts are swapped depending on endian mode,
> - * so define a macro (similar to mips linux32) to handle that.
> - */
> -#ifdef __LITTLE_ENDIAN__
> -#define merge_64(low, high) ((u64)high << 32) | low
> -#else
> -#define merge_64(high, low) ((u64)high << 32) | low
> -#endif
> -
>  compat_ssize_t compat_sys_pread64(unsigned int fd, char __user *ubuf, compat_size_t count,
>  			     u32 reg6, u32 pos1, u32 pos2)
>  {
> @@ -94,7 +82,7 @@ int compat_sys_truncate64(const char __user * path, u32 reg4,
>  long compat_sys_fallocate(int fd, int mode, u32 offset1, u32 offset2,
>  				     u32 len1, u32 len2)
>  {
> -	return ksys_fallocate(fd, mode, ((loff_t)offset1 << 32) | offset2,
> +	return ksys_fallocate(fd, mode, merge_64(offset1, offset2),
>  			     merge_64(len1, len2));
>  }
>  
> diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
> index fc999140bc27..abc3fbb3c490 100644
> --- a/arch/powerpc/kernel/syscalls.c
> +++ b/arch/powerpc/kernel/syscalls.c
> @@ -98,8 +98,8 @@ long ppc64_personality(unsigned long personality)
>  long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
>  		      u32 len_high, u32 len_low)
>  {
> -	return ksys_fadvise64_64(fd, (u64)offset_high << 32 | offset_low,
> -				 (u64)len_high << 32 | len_low, advice);
> +	return ksys_fadvise64_64(fd, merge_64(offset_high, offset_low),
> +				 merge_64(len_high, len_low), advice);
>  }
>  
>  SYSCALL_DEFINE0(switch_endian)
> -- 
> 2.34.1