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Message-Id: <20210301161212.521569141@linuxfoundation.org>
Date: Mon, 1 Mar 2021 17:14:28 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Chris Wilson <chris@...is-wilson.co.uk>,
Kees Cook <keescook@...omium.org>,
Andy Lutomirski <luto@...capital.net>,
Will Drewry <wad@...omium.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Dave Airlie <airlied@...il.com>,
Daniel Vetter <daniel@...ll.ch>,
Lucas Stach <l.stach@...gutronix.de>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Cyrill Gorcunov <gorcunov@...il.com>,
Thomas Zimmermann <tzimmermann@...e.de>,
Daniel Vetter <daniel.vetter@...ll.ch>
Subject: [PATCH 5.10 620/663] kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE
From: Chris Wilson <chris@...is-wilson.co.uk>
commit bfe3911a91047557eb0e620f95a370aee6a248c7 upstream.
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.
Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Kees Cook <keescook@...omium.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Will Drewry <wad@...omium.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Dave Airlie <airlied@...il.com>
Cc: Daniel Vetter <daniel@...ll.ch>
Cc: Lucas Stach <l.stach@...gutronix.de>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Cyrill Gorcunov <gorcunov@...il.com>
Cc: stable@...r.kernel.org
Acked-by: Daniel Vetter <daniel.vetter@...ll.ch> # DRM depends on kcmp
Acked-by: Rasmus Villemoes <linux@...musvillemoes.dk> # systemd uses kcmp
Reviewed-by: Cyrill Gorcunov <gorcunov@...il.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Acked-by: Thomas Zimmermann <tzimmermann@...e.de>
Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210205220012.1983-1-chris@chris-wilson.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
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(-)
--- 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
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1062,7 +1062,7 @@ static struct epitem *ep_find(struct eve
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;
@@ -1104,7 +1104,7 @@ struct file *get_epoll_tfile_raw_ptr(str
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.
--- 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
--- 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
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -48,7 +48,7 @@ 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
--- 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 == ENOSYS)
- SKIP(return, "Kernel does not support kcmp() (missing CONFIG_CHECKPOINT_RESTORE?)");
+ SKIP(return, "Kernel does not support kcmp() (missing CONFIG_KCMP?)");
}
TEST(mode_strict_support)
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