From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions When using eBPF to probe CS CALL instructions within a function, a crash can be triggered. The eBPF tool probes offset 257 of the __hrtimer_run_queues() function: <__hrtimer_run_queues+249>: nopl 0x0(%rax,%rax,1) <__hrtimer_run_queues+254>: mov %r14,%rdi <__hrtimer_run_queues+257>: cs call <__x86_indirect_thunk_r12> <__hrtimer_run_queues+263>: mov %eax,%r12d <__hrtimer_run_queues+266>: xchg %ax,%ax <__hrtimer_run_queues+268>: mov %r13,%rdi Which triggers this crash: BUG: unable to handle page fault for address: 00000000000f41c9 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P RIP: 0010:__hrtimer_run_queues+0x106/0x230 Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is at the 6th byte of the above CS CALL instruction. Since the CS CALL instruction occupies 6 bytes, the exception occurred in the middle of that call instruction. The root cause is that when using eBPF tools to probe in the middle of a function, a kprobe with INT3 is used as the underlying implementation. During single-step emulation of the original CALL instruction, int3_emulate_call() assumes that the probed CALL instruction is 5 bytes long. However, the actual CS-prefixed CALL instruction occupies 6 bytes, so it constructs an incorrect exception return address. When the CPU returns from the kprobe handler, the next instruction to be executed is at the address of the last byte of that CS CALL instruction. Coincidentally, starting from that address, the CPU fetches and decodes a completely different instruction, which ultimately triggers a kernel crash. Fix the issue by using the actual instruction length obtained from the instruction decoder when constructing the exception return address, rather than relying on the hardcoded CALL_INSN_SIZE macro. [ mingo: Refined the changelog ] Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step") Suggested-by: Masami Hiramatsu (Google) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- drivers/dma-buf/Kconfig | 71 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) create mode 100644 drivers/dma-buf/Kconfig (limited to 'drivers/dma-buf/Kconfig') diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig new file mode 100644 index 000000000..7efc0f0d0 --- /dev/null +++ b/drivers/dma-buf/Kconfig @@ -0,0 +1,71 @@ +# SPDX-License-Identifier: GPL-2.0-only +menu "DMABUF options" + +config SYNC_FILE + bool "Explicit Synchronization Framework" + default n + select DMA_SHARED_BUFFER + help + The Sync File Framework adds explicit synchronization via + userspace. It enables send/receive 'struct dma_fence' objects to/from + userspace via Sync File fds for synchronization between drivers via + userspace components. It has been ported from Android. + + The first and main user for this is graphics in which a fence is + associated with a buffer. When a job is submitted to the GPU a fence + is attached to the buffer and is transferred via userspace, using Sync + Files fds, to the DRM driver for example. More details at + Documentation/driver-api/sync_file.rst. + +config SW_SYNC + bool "Sync File Validation Framework" + default n + depends on SYNC_FILE + depends on DEBUG_FS + help + A sync object driver that uses a 32bit counter to coordinate + synchronization. Useful when there is no hardware primitive backing + the synchronization. + + WARNING: improper use of this can result in deadlocking kernel + drivers from userspace. Intended for test and debug only. + +config UDMABUF + bool "userspace dmabuf misc driver" + default n + depends on DMA_SHARED_BUFFER + depends on MEMFD_CREATE || COMPILE_TEST + depends on MMU + help + A driver to let userspace turn memfd regions into dma-bufs. + Qemu can use this to create host dmabufs for guest framebuffers. + +config DMABUF_DEBUG + bool "DMA-BUF debug checks" + depends on DMA_SHARED_BUFFER + default y if DEBUG + help + This option enables additional checks for DMA-BUF importers and + exporters. Specifically it validates that importers do not peek at the + underlying struct page when they import a buffer. + +config DMABUF_KUNIT_TEST + tristate "KUnit tests for DMA-BUF" if !KUNIT_ALL_TESTS + depends on KUNIT + select DMA_SHARED_BUFFER + default KUNIT_ALL_TESTS + help + Enable kunit tests for DMA-BUF + +menuconfig DMABUF_HEAPS + bool "DMA-BUF Userland Memory Heaps" + select DMA_SHARED_BUFFER + help + Choose this option to enable the DMA-BUF userland memory heaps. + This options creates per heap chardevs in /dev/dma_heap/ which + allows userspace to allocate dma-bufs that can be shared + between drivers. + +source "drivers/dma-buf/heaps/Kconfig" + +endmenu -- cgit v1.3.1