This is a note to let you know that I've just added the patch titled kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE to the 5.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kcmp-support-selection-of-sys_kcmp-without-checkpoint_restore.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From bfe3911a91047557eb0e620f95a370aee6a248c7 Mon Sep 17 00:00:00 2001 From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Date: Fri, 5 Feb 2021 22:00:12 +0000 Subject: kcmp: Support selection of SYS_kcmp without CHECKPOINT_RESTORE From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> 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. References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046 Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: Will Drewry <wad@xxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Dave Airlie <airlied@xxxxxxxxx> Cc: Daniel Vetter <daniel@xxxxxxxx> Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx> Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx> # DRM depends on kcmp Acked-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> # systemd uses kcmp Reviewed-by: Cyrill Gorcunov <gorcunov@xxxxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Acked-by: Thomas Zimmermann <tzimmermann@xxxxxxx> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20210205220012.1983-1-chris@xxxxxxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -979,7 +979,7 @@ 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; @@ -1021,7 +1021,7 @@ 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 @@ -1193,6 +1193,7 @@ 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. @@ -1736,6 +1737,16 @@ 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 @@ -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 --- 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) Patches currently in stable-queue which might be from chris@xxxxxxxxxxxxxxxxxx are queue-5.11/drm-modes-switch-to-64bit-maths-to-avoid-integer-overflow.patch queue-5.11/kcmp-support-selection-of-sys_kcmp-without-checkpoint_restore.patch queue-5.11/drm-i915-gt-correct-surface-base-address-for-renderclear.patch queue-5.11/drm-i915-gt-flush-before-changing-register-state.patch queue-5.11/drm-i915-gt-one-more-flush-for-baytrail-clear-residuals.patch