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Message-ID: <20200919053716.GJ30063@infradead.org>
Date: Sat, 19 Sep 2020 06:37:16 +0100
From: Christoph Hellwig <hch@...radead.org>
To: Arnd Bergmann <arnd@...db.de>
Cc: Christoph Hellwig <hch@...radead.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Eric Biederman <ebiederm@...ssion.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-arch@...r.kernel.org, linux-mm@...ck.org,
kexec@...ts.infradead.org
Subject: Re: [PATCH 2/4] kexec: remove compat_sys_kexec_load syscall
On Fri, Sep 18, 2020 at 03:24:37PM +0200, Arnd Bergmann wrote:
> The compat version of sys_kexec_load() uses compat_alloc_user_space to
> convert the user-provided arguments into the native format.
>
> Move the conversion into the regular implementation with
> an in_compat_syscall() check to simplify it and avoid the
> compat_alloc_user_space() call.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> arch/arm64/include/asm/unistd32.h | 2 +-
> arch/mips/kernel/syscalls/syscall_n32.tbl | 2 +-
> arch/mips/kernel/syscalls/syscall_o32.tbl | 2 +-
> arch/parisc/kernel/syscalls/syscall.tbl | 2 +-
> arch/powerpc/kernel/syscalls/syscall.tbl | 2 +-
> arch/s390/kernel/syscalls/syscall.tbl | 2 +-
> arch/sparc/kernel/syscalls/syscall.tbl | 2 +-
> arch/x86/entry/syscalls/syscall_32.tbl | 2 +-
> arch/x86/entry/syscalls/syscall_64.tbl | 2 +-
> include/linux/compat.h | 6 --
> include/uapi/asm-generic/unistd.h | 2 +-
> kernel/kexec.c | 75 ++++++-----------------
> 12 files changed, 29 insertions(+), 72 deletions(-)
>
> diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
> index 734860ac7cf9..b6517df74037 100644
> --- a/arch/arm64/include/asm/unistd32.h
> +++ b/arch/arm64/include/asm/unistd32.h
> @@ -705,7 +705,7 @@ __SYSCALL(__NR_getcpu, sys_getcpu)
> #define __NR_epoll_pwait 346
> __SYSCALL(__NR_epoll_pwait, compat_sys_epoll_pwait)
> #define __NR_kexec_load 347
> -__SYSCALL(__NR_kexec_load, compat_sys_kexec_load)
> +__SYSCALL(__NR_kexec_load, sys_kexec_load)
> #define __NR_utimensat 348
> __SYSCALL(__NR_utimensat, sys_utimensat_time32)
> #define __NR_signalfd 349
> diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
> index f9df9edb67a4..ad157aab4c09 100644
> --- a/arch/mips/kernel/syscalls/syscall_n32.tbl
> +++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
> @@ -282,7 +282,7 @@
> 271 n32 move_pages compat_sys_move_pages
> 272 n32 set_robust_list compat_sys_set_robust_list
> 273 n32 get_robust_list compat_sys_get_robust_list
> -274 n32 kexec_load compat_sys_kexec_load
> +274 n32 kexec_load sys_kexec_load
> 275 n32 getcpu sys_getcpu
> 276 n32 epoll_pwait compat_sys_epoll_pwait
> 277 n32 ioprio_set sys_ioprio_set
> diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
> index 195b43cf27c8..57baf6c8008f 100644
> --- a/arch/mips/kernel/syscalls/syscall_o32.tbl
> +++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
> @@ -322,7 +322,7 @@
> 308 o32 move_pages sys_move_pages compat_sys_move_pages
> 309 o32 set_robust_list sys_set_robust_list compat_sys_set_robust_list
> 310 o32 get_robust_list sys_get_robust_list compat_sys_get_robust_list
> -311 o32 kexec_load sys_kexec_load compat_sys_kexec_load
> +311 o32 kexec_load sys_kexec_load
> 312 o32 getcpu sys_getcpu
> 313 o32 epoll_pwait sys_epoll_pwait compat_sys_epoll_pwait
> 314 o32 ioprio_set sys_ioprio_set
> diff --git a/arch/parisc/kernel/syscalls/syscall.tbl b/arch/parisc/kernel/syscalls/syscall.tbl
> index def64d221cd4..778bf166d7bd 100644
> --- a/arch/parisc/kernel/syscalls/syscall.tbl
> +++ b/arch/parisc/kernel/syscalls/syscall.tbl
> @@ -336,7 +336,7 @@
> 297 common epoll_pwait sys_epoll_pwait compat_sys_epoll_pwait
> 298 common statfs64 sys_statfs64 compat_sys_statfs64
> 299 common fstatfs64 sys_fstatfs64 compat_sys_fstatfs64
> -300 common kexec_load sys_kexec_load compat_sys_kexec_load
> +300 common kexec_load sys_kexec_load
> 301 32 utimensat sys_utimensat_time32
> 301 64 utimensat sys_utimensat
> 302 common signalfd sys_signalfd compat_sys_signalfd
> diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
> index c2d737ff2e7b..f128ba8b9a71 100644
> --- a/arch/powerpc/kernel/syscalls/syscall.tbl
> +++ b/arch/powerpc/kernel/syscalls/syscall.tbl
> @@ -350,7 +350,7 @@
> 265 64 mq_timedreceive sys_mq_timedreceive
> 266 nospu mq_notify sys_mq_notify compat_sys_mq_notify
> 267 nospu mq_getsetattr sys_mq_getsetattr compat_sys_mq_getsetattr
> -268 nospu kexec_load sys_kexec_load compat_sys_kexec_load
> +268 nospu kexec_load sys_kexec_load
> 269 nospu add_key sys_add_key
> 270 nospu request_key sys_request_key
> 271 nospu keyctl sys_keyctl compat_sys_keyctl
> diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
> index 10456bc936fb..d45952058be2 100644
> --- a/arch/s390/kernel/syscalls/syscall.tbl
> +++ b/arch/s390/kernel/syscalls/syscall.tbl
> @@ -283,7 +283,7 @@
> 274 common mq_timedreceive sys_mq_timedreceive sys_mq_timedreceive_time32
> 275 common mq_notify sys_mq_notify compat_sys_mq_notify
> 276 common mq_getsetattr sys_mq_getsetattr compat_sys_mq_getsetattr
> -277 common kexec_load sys_kexec_load compat_sys_kexec_load
> +277 common kexec_load sys_kexec_load sys_kexec_load
> 278 common add_key sys_add_key sys_add_key
> 279 common request_key sys_request_key sys_request_key
> 280 common keyctl sys_keyctl compat_sys_keyctl
> diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
> index 4af114e84f20..a46edcdd950d 100644
> --- a/arch/sparc/kernel/syscalls/syscall.tbl
> +++ b/arch/sparc/kernel/syscalls/syscall.tbl
> @@ -369,7 +369,7 @@
> 303 common mbind sys_mbind compat_sys_mbind
> 304 common get_mempolicy sys_get_mempolicy compat_sys_get_mempolicy
> 305 common set_mempolicy sys_set_mempolicy compat_sys_set_mempolicy
> -306 common kexec_load sys_kexec_load compat_sys_kexec_load
> +306 common kexec_load sys_kexec_load sys_kexec_load
> 307 common move_pages sys_move_pages compat_sys_move_pages
> 308 common getcpu sys_getcpu
> 309 common epoll_pwait sys_epoll_pwait compat_sys_epoll_pwait
> diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
> index 3db3d8823dc8..7e4140b78aad 100644
> --- a/arch/x86/entry/syscalls/syscall_32.tbl
> +++ b/arch/x86/entry/syscalls/syscall_32.tbl
> @@ -294,7 +294,7 @@
> 280 i386 mq_timedreceive sys_mq_timedreceive_time32
> 281 i386 mq_notify sys_mq_notify compat_sys_mq_notify
> 282 i386 mq_getsetattr sys_mq_getsetattr compat_sys_mq_getsetattr
> -283 i386 kexec_load sys_kexec_load compat_sys_kexec_load
> +283 i386 kexec_load sys_kexec_load sys_kexec_load
> 284 i386 waitid sys_waitid compat_sys_waitid
> # 285 sys_setaltroot
> 286 i386 add_key sys_add_key
> diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
> index f30d6ae9a688..9986f5f08278 100644
> --- a/arch/x86/entry/syscalls/syscall_64.tbl
> +++ b/arch/x86/entry/syscalls/syscall_64.tbl
> @@ -384,7 +384,7 @@
> 525 x32 sigaltstack compat_sys_sigaltstack
> 526 x32 timer_create compat_sys_timer_create
> 527 x32 mq_notify compat_sys_mq_notify
> -528 x32 kexec_load compat_sys_kexec_load
> +528 x32 kexec_load sys_kexec_load
> 529 x32 waitid compat_sys_waitid
> 530 x32 set_robust_list compat_sys_set_robust_list
> 531 x32 get_robust_list compat_sys_get_robust_list
> diff --git a/include/linux/compat.h b/include/linux/compat.h
> index 3d96a841bd49..a7a5a0ff59ef 100644
> --- a/include/linux/compat.h
> +++ b/include/linux/compat.h
> @@ -643,12 +643,6 @@ asmlinkage long compat_sys_setitimer(int which,
> struct old_itimerval32 __user *in,
> struct old_itimerval32 __user *out);
>
> -/* kernel/kexec.c */
> -asmlinkage long compat_sys_kexec_load(compat_ulong_t entry,
> - compat_ulong_t nr_segments,
> - struct compat_kexec_segment __user *,
> - compat_ulong_t flags);
> -
> /* kernel/posix-timers.c */
> asmlinkage long compat_sys_timer_create(clockid_t which_clock,
> struct compat_sigevent __user *timer_event_spec,
> diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
> index 995b36c2ea7d..83f1fc7fd3d7 100644
> --- a/include/uapi/asm-generic/unistd.h
> +++ b/include/uapi/asm-generic/unistd.h
> @@ -342,7 +342,7 @@ __SC_COMP(__NR_setitimer, sys_setitimer, compat_sys_setitimer)
>
> /* kernel/kexec.c */
> #define __NR_kexec_load 104
> -__SC_COMP(__NR_kexec_load, sys_kexec_load, compat_sys_kexec_load)
> +__SYSCALL(__NR_kexec_load, sys_kexec_load)
>
> /* kernel/module.c */
> #define __NR_init_module 105
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index f977786fe498..1ef7d3dc906f 100644
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -29,7 +29,25 @@ static int copy_user_segment_list(struct kimage *image,
> /* Read in the segments */
> image->nr_segments = nr_segments;
> segment_bytes = nr_segments * sizeof(*segments);
> - ret = copy_from_user(image->segment, segments, segment_bytes);
> + if (in_compat_syscall()) {
> + struct compat_kexec_segment __user *cs = (void __user *)segments;
> + struct compat_kexec_segment segment;
> + int i;
> + for (i=0; i< nr_segments; i++) {
Missing empty line after the variable declarations and really strange
indentation.
> + copy_from_user(&segment, &cs[i], sizeof(segment));
Missing return value check.
> + if (ret)
> + break;
> +
> + image->segment[i] = (struct kexec_segment) {
> + .buf = compat_ptr(segment.buf),
> + .bufsz = segment.bufsz,
> + .mem = segment.mem,
> + .memsz = segment.memsz,
> + };
> + }
I'd split the whole compat handling into a helper, and I'd probably
use the unsafe_get/put user to optimize it a little more.
> + } else {
> + ret = copy_from_user(image->segment, segments, segment_bytes);
> + }
> if (ret)
> ret = -EFAULT;
Why not just
if (copy_from_user(image->segment, segments, segment_bytes))
ret = -EFAULT;
?
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