Re: [PATCH v3] kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
On Mon, Feb 08, 2021 at 02:12:00PM -0800, Kees Cook wrote:
> On Fri, Feb 05, 2021 at 10:00:12PM +, Chris Wilson wrote:
> > Userspace has discovered the functionality offered by SYS_kcmp and has
> > started to depend upon it. In particular, Mesa uses SYS_kcmp for
> > os_same_file_description() in order to identify when two fd (e.g. device
> > or dmabuf) point to the same struct file. Since they depend on it for
> > core functionality, lift SYS_kcmp out of the non-default
> > CONFIG_CHECKPOINT_RESTORE into the selectable syscall category.
> >
> > Rasmus Villemoes also pointed out that systemd uses SYS_kcmp to
> > deduplicate the per-service file descriptor store.
> >
> > Note that some distributions such as Ubuntu are already enabling
> > CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp.
> >
> > References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046
> > Signed-off-by: Chris Wilson
>
> Thanks!
>
> Reviewed-by: Kees Cook
Thanks for reviews, I stuffed it into a topic branch and plan to
send it to Linus later this week.
Cheers, Daniel
>
> -Kees
>
> > Cc: Kees Cook
> > Cc: Andy Lutomirski
> > Cc: Will Drewry
> > Cc: Andrew Morton
> > Cc: Dave Airlie
> > Cc: Daniel Vetter
> > Cc: Lucas Stach
> > Cc: Rasmus Villemoes
> > Cc: Cyrill Gorcunov
> > Cc: sta...@vger.kernel.org
> > Acked-by: Daniel Vetter # DRM depends on kcmp
> > Acked-by: Rasmus Villemoes # systemd uses kcmp
> >
> > ---
> > v2:
> > - Default n.
> > - Borrrow help message from man kcmp.
> > - Export get_epoll_tfile_raw_ptr() for CONFIG_KCMP
> > v3:
> > - Select KCMP for CONFIG_DRM
> > ---
> > drivers/gpu/drm/Kconfig | 3 +++
> > fs/eventpoll.c| 4 ++--
> > include/linux/eventpoll.h | 2 +-
> > init/Kconfig | 11 +++
> > kernel/Makefile | 2 +-
> > tools/testing/selftests/seccomp/seccomp_bpf.c | 2 +-
> > 6 files changed, 19 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> > index 0973f408d75f..af6c6d214d91 100644
> > --- a/drivers/gpu/drm/Kconfig
> > +++ b/drivers/gpu/drm/Kconfig
> > @@ -15,6 +15,9 @@ menuconfig DRM
> > select I2C_ALGOBIT
> > select DMA_SHARED_BUFFER
> > select SYNC_FILE
> > +# gallium uses SYS_kcmp for os_same_file_description() to de-duplicate
> > +# device and dmabuf fd. Let's make sure that is available for our
> > userspace.
> > + select KCMP
> > help
> > Kernel-level support for the Direct Rendering Infrastructure (DRI)
> > introduced in XFree86 4.0. If you say Y here, you need to select
> > diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> > index a829af074eb5..3196474cbe24 100644
> > --- a/fs/eventpoll.c
> > +++ b/fs/eventpoll.c
> > @@ -979,7 +979,7 @@ static struct epitem *ep_find(struct eventpoll *ep,
> > struct file *file, int fd)
> > return epir;
> > }
> >
> > -#ifdef CONFIG_CHECKPOINT_RESTORE
> > +#ifdef CONFIG_KCMP
> > static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned
> > long toff)
> > {
> > struct rb_node *rbp;
> > @@ -1021,7 +1021,7 @@ struct file *get_epoll_tfile_raw_ptr(struct file
> > *file, int tfd,
> >
> > return file_raw;
> > }
> > -#endif /* CONFIG_CHECKPOINT_RESTORE */
> > +#endif /* CONFIG_KCMP */
> >
> > /**
> > * Adds a new entry to the tail of the list in a lockless way, i.e.
> > diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
> > index 0350393465d4..593322c946e6 100644
> > --- a/include/linux/eventpoll.h
> > +++ b/include/linux/eventpoll.h
> > @@ -18,7 +18,7 @@ struct file;
> >
> > #ifdef CONFIG_EPOLL
> >
> > -#ifdef CONFIG_CHECKPOINT_RESTORE
> > +#ifdef CONFIG_KCMP
> > struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned
> > long toff);
> > #endif
> >
> > diff --git a/init/Kconfig b/init/Kconfig
> > index b77c60f8b963..9cc7436b2f73 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -1194,6 +1194,7 @@ endif # NAMESPACES
> > config CHECKPOINT_RESTORE
> > bool "Checkpoint/restore support"
> > select PROC_CHILDREN
> > + select KCMP
> > default n
> > help
> > Enables additional kernel features in a sake of checkpoint/restore.
> > @@ -1737,6 +1738,16 @@ config ARCH_HAS_MEMBARRIER_CALLBACKS
> > config ARCH_HAS_MEMBARRIER_SYNC_CORE
> > bool
> >
> > +config KCMP
> > + bool "Enable kcmp() system call" if EXPERT
> > + help
> > + Enable the kernel resource comparison system call. It provides
> > + user-space with the ability to compare two processes to see if they
> > + share a common resource, such as a file descriptor or even virtual
> > + memory space.
> > +
> > + If unsure, say N.
> > +
> > config RSEQ
> > bool "Enable rseq() system call" if EXPERT
> > default y
> > diff --git a/kernel/Makefile b/kernel/Makefile
> > index
Re: [PATCH v3] kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
Hi
Am 05.02.21 um 23:00 schrieb Chris Wilson:
Userspace has discovered the functionality offered by SYS_kcmp and has
started to depend upon it. In particular, Mesa uses SYS_kcmp for
os_same_file_description() in order to identify when two fd (e.g. device
or dmabuf) point to the same struct file. Since they depend on it for
core functionality, lift SYS_kcmp out of the non-default
CONFIG_CHECKPOINT_RESTORE into the selectable syscall category.
Rasmus Villemoes also pointed out that systemd uses SYS_kcmp to
deduplicate the per-service file descriptor store.
This helps a lot with transactional programming in userspace system
code. So FWIW
Acked-by: Thomas Zimmermann
Note that some distributions such as Ubuntu are already enabling
CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp.
References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046
Signed-off-by: Chris Wilson
Cc: Kees Cook
Cc: Andy Lutomirski
Cc: Will Drewry
Cc: Andrew Morton
Cc: Dave Airlie
Cc: Daniel Vetter
Cc: Lucas Stach
Cc: Rasmus Villemoes
Cc: Cyrill Gorcunov
Cc: sta...@vger.kernel.org
Acked-by: Daniel Vetter # DRM depends on kcmp
Acked-by: Rasmus Villemoes # systemd uses kcmp
---
v2:
- Default n.
- Borrrow help message from man kcmp.
- Export get_epoll_tfile_raw_ptr() for CONFIG_KCMP
v3:
- Select KCMP for CONFIG_DRM
---
drivers/gpu/drm/Kconfig | 3 +++
fs/eventpoll.c| 4 ++--
include/linux/eventpoll.h | 2 +-
init/Kconfig | 11 +++
kernel/Makefile | 2 +-
tools/testing/selftests/seccomp/seccomp_bpf.c | 2 +-
6 files changed, 19 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 0973f408d75f..af6c6d214d91 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -15,6 +15,9 @@ menuconfig DRM
select I2C_ALGOBIT
select DMA_SHARED_BUFFER
select SYNC_FILE
+# gallium uses SYS_kcmp for os_same_file_description() to de-duplicate
+# device and dmabuf fd. Let's make sure that is available for our userspace.
+ select KCMP
help
Kernel-level support for the Direct Rendering Infrastructure (DRI)
introduced in XFree86 4.0. If you say Y here, you need to select
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index a829af074eb5..3196474cbe24 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -979,7 +979,7 @@ static struct epitem *ep_find(struct eventpoll *ep, struct
file *file, int fd)
return epir;
}
-#ifdef CONFIG_CHECKPOINT_RESTORE
+#ifdef CONFIG_KCMP
static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned
long toff)
{
struct rb_node *rbp;
@@ -1021,7 +1021,7 @@ struct file *get_epoll_tfile_raw_ptr(struct file *file,
int tfd,
return file_raw;
}
-#endif /* CONFIG_CHECKPOINT_RESTORE */
+#endif /* CONFIG_KCMP */
/**
* Adds a new entry to the tail of the list in a lockless way, i.e.
diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
index 0350393465d4..593322c946e6 100644
--- a/include/linux/eventpoll.h
+++ b/include/linux/eventpoll.h
@@ -18,7 +18,7 @@ struct file;
#ifdef CONFIG_EPOLL
-#ifdef CONFIG_CHECKPOINT_RESTORE
+#ifdef CONFIG_KCMP
struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned
long toff);
#endif
diff --git a/init/Kconfig b/init/Kconfig
index b77c60f8b963..9cc7436b2f73 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1194,6 +1194,7 @@ endif # NAMESPACES
config CHECKPOINT_RESTORE
bool "Checkpoint/restore support"
select PROC_CHILDREN
+ select KCMP
default n
help
Enables additional kernel features in a sake of checkpoint/restore.
@@ -1737,6 +1738,16 @@ config ARCH_HAS_MEMBARRIER_CALLBACKS
config ARCH_HAS_MEMBARRIER_SYNC_CORE
bool
+config KCMP
+ bool "Enable kcmp() system call" if EXPERT
+ help
+ Enable the kernel resource comparison system call. It provides
+ user-space with the ability to compare two processes to see if they
+ share a common resource, such as a file descriptor or even virtual
+ memory space.
+
+ If unsure, say N.
+
config RSEQ
bool "Enable rseq() system call" if EXPERT
default y
diff --git a/kernel/Makefile b/kernel/Makefile
index aa7368c7eabf..320f1f3941b7 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -51,7 +51,7 @@ obj-y += livepatch/
obj-y += dma/
obj-y += entry/
-obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o
+obj-$(CONFIG_KCMP) += kcmp.o
obj-$(CONFIG_FREEZER) += freezer.o
obj-$(CONFIG_PROFILING) += profile.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c
b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 26c72f2b61b1..1b6c7d33c4ff 100644
---
Re: [PATCH v3] kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
On Fri, 12 Feb 2021 at 14:01, Michel Dänzer wrote: > > On 2021-02-12 1:57 p.m., Emil Velikov wrote: > > On Fri, 5 Feb 2021 at 22:01, Chris Wilson wrote: > >> > >> Userspace has discovered the functionality offered by SYS_kcmp and has > >> started to depend upon it. In particular, Mesa uses SYS_kcmp for > >> os_same_file_description() in order to identify when two fd (e.g. device > >> or dmabuf) > > > > As you rightfully point out, SYS_kcmp is a bit of a two edged sword. > > While you mention the CONFIG issue, there is also a portability aspect > > (mesa runs on more than just linux) and as well as sandbox filtering > > of the extra syscall. > > > > Last time I looked, the latter was still an issue and mesa was using > > SYS_kcmp to compare device node fds. > > A far shorter and more portable solution is possible, so let me > > prepare a Mesa patch. > > Make sure to read my comments on > https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6881 first. :) > Much appreciated. I might have been "slightly" off - pardon for the noise o/ -Emil
Re: [PATCH v3] kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
On Fri, 12 Feb 2021 at 13:14, Simon Ser wrote: > > On Friday, February 12th, 2021 at 1:57 PM, Emil Velikov > wrote: > > > On Fri, 5 Feb 2021 at 22:01, Chris Wilson wrote: > > > > > > Userspace has discovered the functionality offered by SYS_kcmp and has > > > started to depend upon it. In particular, Mesa uses SYS_kcmp for > > > os_same_file_description() in order to identify when two fd (e.g. device > > > or dmabuf) > > > > As you rightfully point out, SYS_kcmp is a bit of a two edged sword. > > While you mention the CONFIG issue, there is also a portability aspect > > (mesa runs on more than just linux) and as well as sandbox filtering > > of the extra syscall. > > > > Last time I looked, the latter was still an issue and mesa was using > > SYS_kcmp to compare device node fds. > > A far shorter and more portable solution is possible, so let me > > prepare a Mesa patch. > > Comparing two DMA-BUFs can be done with their inode number, I think. > > Comparing two device FDs is more subtle, because of GEM handle > ref'counting. You sometimes really want to check whether two FDs are > backed by the same file *description*. See [1] for details. > Thanks for the correction and the reference. Seems like I've short circuited file description table vs file descriptor. Emil
Re: [PATCH v3] kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
On 2021-02-12 1:57 p.m., Emil Velikov wrote: On Fri, 5 Feb 2021 at 22:01, Chris Wilson wrote: Userspace has discovered the functionality offered by SYS_kcmp and has started to depend upon it. In particular, Mesa uses SYS_kcmp for os_same_file_description() in order to identify when two fd (e.g. device or dmabuf) As you rightfully point out, SYS_kcmp is a bit of a two edged sword. While you mention the CONFIG issue, there is also a portability aspect (mesa runs on more than just linux) and as well as sandbox filtering of the extra syscall. Last time I looked, the latter was still an issue and mesa was using SYS_kcmp to compare device node fds. A far shorter and more portable solution is possible, so let me prepare a Mesa patch. Make sure to read my comments on https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6881 first. :) -- Earthling Michel Dänzer | https://redhat.com Libre software enthusiast | Mesa and X developer
Re: [PATCH v3] kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
On Friday, February 12th, 2021 at 1:57 PM, Emil Velikov wrote: > On Fri, 5 Feb 2021 at 22:01, Chris Wilson wrote: > > > > Userspace has discovered the functionality offered by SYS_kcmp and has > > started to depend upon it. In particular, Mesa uses SYS_kcmp for > > os_same_file_description() in order to identify when two fd (e.g. device > > or dmabuf) > > As you rightfully point out, SYS_kcmp is a bit of a two edged sword. > While you mention the CONFIG issue, there is also a portability aspect > (mesa runs on more than just linux) and as well as sandbox filtering > of the extra syscall. > > Last time I looked, the latter was still an issue and mesa was using > SYS_kcmp to compare device node fds. > A far shorter and more portable solution is possible, so let me > prepare a Mesa patch. Comparing two DMA-BUFs can be done with their inode number, I think. Comparing two device FDs is more subtle, because of GEM handle ref'counting. You sometimes really want to check whether two FDs are backed by the same file *description*. See [1] for details. [1]: https://gitlab.freedesktop.org/mesa/drm/-/merge_requests/110
Re: [PATCH v3] kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
On Fri, 5 Feb 2021 at 22:01, Chris Wilson wrote: > > Userspace has discovered the functionality offered by SYS_kcmp and has > started to depend upon it. In particular, Mesa uses SYS_kcmp for > os_same_file_description() in order to identify when two fd (e.g. device > or dmabuf) As you rightfully point out, SYS_kcmp is a bit of a two edged sword. While you mention the CONFIG issue, there is also a portability aspect (mesa runs on more than just linux) and as well as sandbox filtering of the extra syscall. Last time I looked, the latter was still an issue and mesa was using SYS_kcmp to compare device node fds. A far shorter and more portable solution is possible, so let me prepare a Mesa patch. -Emil
Re: [PATCH v3] kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
On Fri, Feb 05, 2021 at 10:00:12PM +, Chris Wilson wrote:
> Userspace has discovered the functionality offered by SYS_kcmp and has
> started to depend upon it. In particular, Mesa uses SYS_kcmp for
> os_same_file_description() in order to identify when two fd (e.g. device
> or dmabuf) point to the same struct file. Since they depend on it for
> core functionality, lift SYS_kcmp out of the non-default
> CONFIG_CHECKPOINT_RESTORE into the selectable syscall category.
>
> Rasmus Villemoes also pointed out that systemd uses SYS_kcmp to
> deduplicate the per-service file descriptor store.
>
> Note that some distributions such as Ubuntu are already enabling
> CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp.
>
> References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046
> Signed-off-by: Chris Wilson
Thanks!
Reviewed-by: Kees Cook
-Kees
> Cc: Kees Cook
> Cc: Andy Lutomirski
> Cc: Will Drewry
> Cc: Andrew Morton
> Cc: Dave Airlie
> Cc: Daniel Vetter
> Cc: Lucas Stach
> Cc: Rasmus Villemoes
> Cc: Cyrill Gorcunov
> Cc: sta...@vger.kernel.org
> Acked-by: Daniel Vetter # DRM depends on kcmp
> Acked-by: Rasmus Villemoes # systemd uses kcmp
>
> ---
> v2:
> - Default n.
> - Borrrow help message from man kcmp.
> - Export get_epoll_tfile_raw_ptr() for CONFIG_KCMP
> v3:
> - Select KCMP for CONFIG_DRM
> ---
> drivers/gpu/drm/Kconfig | 3 +++
> fs/eventpoll.c| 4 ++--
> include/linux/eventpoll.h | 2 +-
> init/Kconfig | 11 +++
> kernel/Makefile | 2 +-
> tools/testing/selftests/seccomp/seccomp_bpf.c | 2 +-
> 6 files changed, 19 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 0973f408d75f..af6c6d214d91 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -15,6 +15,9 @@ menuconfig DRM
> select I2C_ALGOBIT
> select DMA_SHARED_BUFFER
> select SYNC_FILE
> +# gallium uses SYS_kcmp for os_same_file_description() to de-duplicate
> +# device and dmabuf fd. Let's make sure that is available for our userspace.
> + select KCMP
> help
> Kernel-level support for the Direct Rendering Infrastructure (DRI)
> introduced in XFree86 4.0. If you say Y here, you need to select
> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> index a829af074eb5..3196474cbe24 100644
> --- a/fs/eventpoll.c
> +++ b/fs/eventpoll.c
> @@ -979,7 +979,7 @@ static struct epitem *ep_find(struct eventpoll *ep,
> struct file *file, int fd)
> return epir;
> }
>
> -#ifdef CONFIG_CHECKPOINT_RESTORE
> +#ifdef CONFIG_KCMP
> static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned
> long toff)
> {
> struct rb_node *rbp;
> @@ -1021,7 +1021,7 @@ struct file *get_epoll_tfile_raw_ptr(struct file *file,
> int tfd,
>
> return file_raw;
> }
> -#endif /* CONFIG_CHECKPOINT_RESTORE */
> +#endif /* CONFIG_KCMP */
>
> /**
> * Adds a new entry to the tail of the list in a lockless way, i.e.
> diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
> index 0350393465d4..593322c946e6 100644
> --- a/include/linux/eventpoll.h
> +++ b/include/linux/eventpoll.h
> @@ -18,7 +18,7 @@ struct file;
>
> #ifdef CONFIG_EPOLL
>
> -#ifdef CONFIG_CHECKPOINT_RESTORE
> +#ifdef CONFIG_KCMP
> struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned
> long toff);
> #endif
>
> diff --git a/init/Kconfig b/init/Kconfig
> index b77c60f8b963..9cc7436b2f73 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1194,6 +1194,7 @@ endif # NAMESPACES
> config CHECKPOINT_RESTORE
> bool "Checkpoint/restore support"
> select PROC_CHILDREN
> + select KCMP
> default n
> help
> Enables additional kernel features in a sake of checkpoint/restore.
> @@ -1737,6 +1738,16 @@ config ARCH_HAS_MEMBARRIER_CALLBACKS
> config ARCH_HAS_MEMBARRIER_SYNC_CORE
> bool
>
> +config KCMP
> + bool "Enable kcmp() system call" if EXPERT
> + help
> + Enable the kernel resource comparison system call. It provides
> + user-space with the ability to compare two processes to see if they
> + share a common resource, such as a file descriptor or even virtual
> + memory space.
> +
> + If unsure, say N.
> +
> config RSEQ
> bool "Enable rseq() system call" if EXPERT
> default y
> diff --git a/kernel/Makefile b/kernel/Makefile
> index aa7368c7eabf..320f1f3941b7 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -51,7 +51,7 @@ obj-y += livepatch/
> obj-y += dma/
> obj-y += entry/
>
> -obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o
> +obj-$(CONFIG_KCMP) += kcmp.o
> obj-$(CONFIG_FREEZER) += freezer.o
> obj-$(CONFIG_PROFILING) += profile.o
> obj-$(CONFIG_STACKTRACE) += stacktrace.o
> diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c
>
Re: [PATCH v3] kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
On Fri, Feb 05, 2021 at 10:00:12PM +, Chris Wilson wrote: > Userspace has discovered the functionality offered by SYS_kcmp and has > started to depend upon it. In particular, Mesa uses SYS_kcmp for > os_same_file_description() in order to identify when two fd (e.g. device > or dmabuf) point to the same struct file. Since they depend on it for > core functionality, lift SYS_kcmp out of the non-default > CONFIG_CHECKPOINT_RESTORE into the selectable syscall category. > ... Reviewed-by: Cyrill Gorcunov
[PATCH v3] kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
Userspace has discovered the functionality offered by SYS_kcmp and has
started to depend upon it. In particular, Mesa uses SYS_kcmp for
os_same_file_description() in order to identify when two fd (e.g. device
or dmabuf) point to the same struct file. Since they depend on it for
core functionality, lift SYS_kcmp out of the non-default
CONFIG_CHECKPOINT_RESTORE into the selectable syscall category.
Rasmus Villemoes also pointed out that systemd uses SYS_kcmp to
deduplicate the per-service file descriptor store.
Note that some distributions such as Ubuntu are already enabling
CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp.
References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046
Signed-off-by: Chris Wilson
Cc: Kees Cook
Cc: Andy Lutomirski
Cc: Will Drewry
Cc: Andrew Morton
Cc: Dave Airlie
Cc: Daniel Vetter
Cc: Lucas Stach
Cc: Rasmus Villemoes
Cc: Cyrill Gorcunov
Cc: sta...@vger.kernel.org
Acked-by: Daniel Vetter # DRM depends on kcmp
Acked-by: Rasmus Villemoes # systemd uses kcmp
---
v2:
- Default n.
- Borrrow help message from man kcmp.
- Export get_epoll_tfile_raw_ptr() for CONFIG_KCMP
v3:
- Select KCMP for CONFIG_DRM
---
drivers/gpu/drm/Kconfig | 3 +++
fs/eventpoll.c| 4 ++--
include/linux/eventpoll.h | 2 +-
init/Kconfig | 11 +++
kernel/Makefile | 2 +-
tools/testing/selftests/seccomp/seccomp_bpf.c | 2 +-
6 files changed, 19 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 0973f408d75f..af6c6d214d91 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -15,6 +15,9 @@ menuconfig DRM
select I2C_ALGOBIT
select DMA_SHARED_BUFFER
select SYNC_FILE
+# gallium uses SYS_kcmp for os_same_file_description() to de-duplicate
+# device and dmabuf fd. Let's make sure that is available for our userspace.
+ select KCMP
help
Kernel-level support for the Direct Rendering Infrastructure (DRI)
introduced in XFree86 4.0. If you say Y here, you need to select
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index a829af074eb5..3196474cbe24 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -979,7 +979,7 @@ static struct epitem *ep_find(struct eventpoll *ep, struct
file *file, int fd)
return epir;
}
-#ifdef CONFIG_CHECKPOINT_RESTORE
+#ifdef CONFIG_KCMP
static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned long
toff)
{
struct rb_node *rbp;
@@ -1021,7 +1021,7 @@ struct file *get_epoll_tfile_raw_ptr(struct file *file,
int tfd,
return file_raw;
}
-#endif /* CONFIG_CHECKPOINT_RESTORE */
+#endif /* CONFIG_KCMP */
/**
* Adds a new entry to the tail of the list in a lockless way, i.e.
diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h
index 0350393465d4..593322c946e6 100644
--- a/include/linux/eventpoll.h
+++ b/include/linux/eventpoll.h
@@ -18,7 +18,7 @@ struct file;
#ifdef CONFIG_EPOLL
-#ifdef CONFIG_CHECKPOINT_RESTORE
+#ifdef CONFIG_KCMP
struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long
toff);
#endif
diff --git a/init/Kconfig b/init/Kconfig
index b77c60f8b963..9cc7436b2f73 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1194,6 +1194,7 @@ endif # NAMESPACES
config CHECKPOINT_RESTORE
bool "Checkpoint/restore support"
select PROC_CHILDREN
+ select KCMP
default n
help
Enables additional kernel features in a sake of checkpoint/restore.
@@ -1737,6 +1738,16 @@ config ARCH_HAS_MEMBARRIER_CALLBACKS
config ARCH_HAS_MEMBARRIER_SYNC_CORE
bool
+config KCMP
+ bool "Enable kcmp() system call" if EXPERT
+ help
+ Enable the kernel resource comparison system call. It provides
+ user-space with the ability to compare two processes to see if they
+ share a common resource, such as a file descriptor or even virtual
+ memory space.
+
+ If unsure, say N.
+
config RSEQ
bool "Enable rseq() system call" if EXPERT
default y
diff --git a/kernel/Makefile b/kernel/Makefile
index aa7368c7eabf..320f1f3941b7 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -51,7 +51,7 @@ obj-y += livepatch/
obj-y += dma/
obj-y += entry/
-obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o
+obj-$(CONFIG_KCMP) += kcmp.o
obj-$(CONFIG_FREEZER) += freezer.o
obj-$(CONFIG_PROFILING) += profile.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c
b/tools/testing/selftests/seccomp/seccomp_bpf.c
index 26c72f2b61b1..1b6c7d33c4ff 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -315,7 +315,7 @@ TEST(kcmp)
ret = __filecmp(getpid(), getpid(), 1, 1);
EXPECT_EQ(ret, 0);
if (ret != 0 && errno ==
