[PATCH] epoll: fix compat syscall wire up of epoll_pwait2

[PATCH] epoll: fix compat syscall wire up of epoll_pwait2

[Heiko Carstens]

Commit b0a0c2615f6f ("epoll: wire up syscall epoll_pwait2") wired up
the 64 bit syscall instead of the compat variant in a couple of places.

Cc: Willem de Bruijn <willemb@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Fixes: b0a0c2615f6f ("epoll: wire up syscall epoll_pwait2")
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 arch/arm64/include/asm/unistd32.h         | 2 +-
 arch/mips/kernel/syscalls/syscall_n32.tbl | 2 +-
 arch/s390/kernel/syscalls/syscall.tbl     | 2 +-
 arch/sparc/kernel/syscalls/syscall.tbl    | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
index f4bca2b90218..cccfbbefbf95 100644
--- a/arch/arm64/include/asm/unistd32.h
+++ b/arch/arm64/include/asm/unistd32.h
@@ -890,7 +890,7 @@ __SYSCALL(__NR_faccessat2, sys_faccessat2)
 #define __NR_process_madvise 440
 __SYSCALL(__NR_process_madvise, sys_process_madvise)
 #define __NR_epoll_pwait2 441
-__SYSCALL(__NR_epoll_pwait2, sys_epoll_pwait2)
+__SYSCALL(__NR_epoll_pwait2, compat_sys_epoll_pwait2)
 
 /*
  * Please add new compat syscalls above this comment and update
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index ad9c3dd0ab1f..0f03ad223f33 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -379,4 +379,4 @@
 438	n32	pidfd_getfd			sys_pidfd_getfd
 439	n32	faccessat2			sys_faccessat2
 440	n32	process_madvise			sys_process_madvise
-441	n32	epoll_pwait2			sys_epoll_pwait2
+441	n32	epoll_pwait2			compat_sys_epoll_pwait2
diff --git a/arch/s390/kernel/syscalls/syscall.tbl b/arch/s390/kernel/syscalls/syscall.tbl
index 14f6525886a8..d443423495e5 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -443,4 +443,4 @@
 438  common	pidfd_getfd		sys_pidfd_getfd			sys_pidfd_getfd
 439  common	faccessat2		sys_faccessat2			sys_faccessat2
 440  common	process_madvise		sys_process_madvise		sys_process_madvise
-441  common	epoll_pwait2		sys_epoll_pwait2		sys_epoll_pwait2
+441  common	epoll_pwait2		sys_epoll_pwait2		compat_sys_epoll_pwait2
diff --git a/arch/sparc/kernel/syscalls/syscall.tbl b/arch/sparc/kernel/syscalls/syscall.tbl
index c7da4c3271e6..40d8c7cd8298 100644
--- a/arch/sparc/kernel/syscalls/syscall.tbl
+++ b/arch/sparc/kernel/syscalls/syscall.tbl
@@ -486,4 +486,4 @@
 438	common	pidfd_getfd			sys_pidfd_getfd
 439	common	faccessat2			sys_faccessat2
 440	common	process_madvise			sys_process_madvise
-441	common	epoll_pwait2			sys_epoll_pwait2
+441	common	epoll_pwait2			sys_epoll_pwait2		compat_sys_epoll_pwait2
-- 
2.17.1

Re: [PATCH] epoll: fix compat syscall wire up of epoll_pwait2

[Arnd Bergmann]

On Sun, Dec 20, 2020 at 11:00 AM Heiko Carstens <hca@linux.ibm.com> wrote:
>
> Commit b0a0c2615f6f ("epoll: wire up syscall epoll_pwait2") wired up
> the 64 bit syscall instead of the compat variant in a couple of places.
>
> Cc: Willem de Bruijn <willemb@google.com>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: Vasily Gorbik <gor@linux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Fixes: b0a0c2615f6f ("epoll: wire up syscall epoll_pwait2")
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> ---
>  arch/arm64/include/asm/unistd32.h         | 2 +-
>  arch/mips/kernel/syscalls/syscall_n32.tbl | 2 +-
>  arch/s390/kernel/syscalls/syscall.tbl     | 2 +-
>  arch/sparc/kernel/syscalls/syscall.tbl    | 2 +-
>  4 files changed, 4 insertions(+), 4 deletions(-)

I double-checked all the entries to make sure you caught all
the missing ones, looks good.

Acked-by: Arnd Bergmann <arnd@arndb.de>

Re: [PATCH] epoll: fix compat syscall wire up of epoll_pwait2

[Willem de Bruijn]

On Sun, Dec 20, 2020 at 6:43 AM Arnd Bergmann <arnd@kernel.org> wrote:
>
> On Sun, Dec 20, 2020 at 11:00 AM Heiko Carstens <hca@linux.ibm.com> wrote:
> >
> > Commit b0a0c2615f6f ("epoll: wire up syscall epoll_pwait2") wired up
> > the 64 bit syscall instead of the compat variant in a couple of places.
> >
> > Cc: Willem de Bruijn <willemb@google.com>
> > Cc: Al Viro <viro@zeniv.linux.org.uk>
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Will Deacon <will@kernel.org>
> > Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> > Cc: Vasily Gorbik <gor@linux.ibm.com>
> > Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> > Cc: "David S. Miller" <davem@davemloft.net>
> > Fixes: b0a0c2615f6f ("epoll: wire up syscall epoll_pwait2")
> > Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> > ---
> >  arch/arm64/include/asm/unistd32.h         | 2 +-
> >  arch/mips/kernel/syscalls/syscall_n32.tbl | 2 +-
> >  arch/s390/kernel/syscalls/syscall.tbl     | 2 +-
> >  arch/sparc/kernel/syscalls/syscall.tbl    | 2 +-
> >  4 files changed, 4 insertions(+), 4 deletions(-)
>
> I double-checked all the entries to make sure you caught all
> the missing ones, looks good.
>
> Acked-by: Arnd Bergmann <arnd@arndb.de>

Acked-by: Willem de Bruijn <willemb@google.com>

Thanks a lot. I also arrived at the same list after comparing to
epoll_pwait and signalfd (for sigset) and ppoll_time64 (for timespec64).

Slightly tangential, it's not immediately clear to me why in
arch/x86/entry/syscalls/syscall_32.tbl epoll_pwait does not need a
compat entry, unlike on other architectures and unlike signalfd.

Re: [PATCH] epoll: fix compat syscall wire up of epoll_pwait2

[Linus Torvalds]

On Sun, Dec 20, 2020 at 10:22 AM Willem de Bruijn
<willemdebruijn.kernel@gmail.com> wrote:
>
> Slightly tangential, it's not immediately clear to me why in
> arch/x86/entry/syscalls/syscall_32.tbl epoll_pwait does not need a
> compat entry, unlike on other architectures and unlike signalfd.

Hmm. Good question. That looks like a bug to me. Probably nobody
noticed because it's so rarely used.

Or maybe I'm missing something too.

Adding x86 entry code people to the participants.

             Linus

Re: [PATCH] epoll: fix compat syscall wire up of epoll_pwait2

[Arnd Bergmann]

On Sun, Dec 20, 2020 at 7:51 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Sun, Dec 20, 2020 at 10:22 AM Willem de Bruijn
> <willemdebruijn.kernel@gmail.com> wrote:
> >
> > Slightly tangential, it's not immediately clear to me why in
> > arch/x86/entry/syscalls/syscall_32.tbl epoll_pwait does not need a
> > compat entry, unlike on other architectures and unlike signalfd.
>
> Hmm. Good question. That looks like a bug to me. Probably nobody
> noticed because it's so rarely used.
>
> Or maybe I'm missing something too.
>
> Adding x86 entry code people to the participants.

The sigset_t argument is actually compatible between x86-32 and x86-64
because

- The bits are in the same order on little-endian machines
- _NSIG is the same as _COMPAT_NSIG (unlike old sparc kernels)
- accessing a 64-bit with 32-bit alignment is always allowed on x86

All other architectures with compat mode support big-endian
code at least as an option, so they have to use the compat
version.

         Arnd

Re: [PATCH] epoll: fix compat syscall wire up of epoll_pwait2

[Linus Torvalds]

On Sun, Dec 20, 2020 at 12:14 PM Arnd Bergmann <arnd@kernel.org> wrote:
>
> The sigset_t argument is actually compatible between x86-32 and x86-64

Well, random high bits in size_t or the pointer value aren't. So it
still looks a bit iffy to me.

But it might end up working almost by accident.

          Linus

Re: [PATCH] epoll: fix compat syscall wire up of epoll_pwait2

[Arnd Bergmann]

On Sun, Dec 20, 2020 at 10:06 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Sun, Dec 20, 2020 at 12:14 PM Arnd Bergmann <arnd@kernel.org> wrote:
> >
> > The sigset_t argument is actually compatible between x86-32 and x86-64
>
> Well, random high bits in size_t or the pointer value aren't. So it
> still looks a bit iffy to me.
>
> But it might end up working almost by accident.

The direct syscall arguments all get the correct zero-extension with
asm/syscall_wrapper.h, just like they do with any other syscall that
is used in both native and compat mode, like epoll_wait().

It probably makes sense to change it just for consistency with the other
architectures, but I would assume that it was intentional when this was
added originally, as the compat handling for epoll_pwait() went through
several iterations before it first worked correctly.

        Arnd

Re: [PATCH] epoll: fix compat syscall wire up of epoll_pwait2

[Will Deacon]

On Sun, Dec 20, 2020 at 10:58:30AM +0100, Heiko Carstens wrote:
> Commit b0a0c2615f6f ("epoll: wire up syscall epoll_pwait2") wired up
> the 64 bit syscall instead of the compat variant in a couple of places.
> 
> Cc: Willem de Bruijn <willemb@google.com>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: Vasily Gorbik <gor@linux.ibm.com>
> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Fixes: b0a0c2615f6f ("epoll: wire up syscall epoll_pwait2")
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> ---
>  arch/arm64/include/asm/unistd32.h         | 2 +-
>  arch/mips/kernel/syscalls/syscall_n32.tbl | 2 +-
>  arch/s390/kernel/syscalls/syscall.tbl     | 2 +-
>  arch/sparc/kernel/syscalls/syscall.tbl    | 2 +-
>  4 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
> index f4bca2b90218..cccfbbefbf95 100644
> --- a/arch/arm64/include/asm/unistd32.h
> +++ b/arch/arm64/include/asm/unistd32.h
> @@ -890,7 +890,7 @@ __SYSCALL(__NR_faccessat2, sys_faccessat2)
>  #define __NR_process_madvise 440
>  __SYSCALL(__NR_process_madvise, sys_process_madvise)
>  #define __NR_epoll_pwait2 441
> -__SYSCALL(__NR_epoll_pwait2, sys_epoll_pwait2)
> +__SYSCALL(__NR_epoll_pwait2, compat_sys_epoll_pwait2)


For this bit ^^

Acked-by: Will Deacon <will@kernel.org>

Will