x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

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) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 276 insertions, 0 deletions

diff --git a/fs/jffs2/debug.h b/fs/jffs2/debug.h
new file mode 100644
index 000000000..40e203b6e
--- /dev/null
+++ b/fs/jffs2/debug.h
@@ -0,0 +1,276 @@
+/*
+ * JFFS2 -- Journalling Flash File System, Version 2.
+ *
+ * Copyright © 2001-2007 Red Hat, Inc.
+ * Copyright © 2004-2010 David Woodhouse <dwmw2@infradead.org>
+ *
+ * Created by David Woodhouse <dwmw2@infradead.org>
+ *
+ * For licensing information, see the file 'LICENCE' in this directory.
+ *
+ */
+
+#ifndef _JFFS2_DEBUG_H_
+#define _JFFS2_DEBUG_H_
+
+#include <linux/printk.h>
+#include <linux/sched.h>
+
+#ifndef CONFIG_JFFS2_FS_DEBUG
+#define CONFIG_JFFS2_FS_DEBUG 0
+#endif
+
+#if CONFIG_JFFS2_FS_DEBUG > 0
+/* Enable "paranoia" checks and dumps */
+#define JFFS2_DBG_PARANOIA_CHECKS
+#define JFFS2_DBG_DUMPS
+
+/*
+ * By defining/undefining the below macros one may select debugging messages
+ * fro specific JFFS2 subsystems.
+ */
+#define JFFS2_DBG_READINODE_MESSAGES
+#define JFFS2_DBG_FRAGTREE_MESSAGES
+#define JFFS2_DBG_DENTLIST_MESSAGES
+#define JFFS2_DBG_NODEREF_MESSAGES
+#define JFFS2_DBG_INOCACHE_MESSAGES
+#define JFFS2_DBG_SUMMARY_MESSAGES
+#define JFFS2_DBG_FSBUILD_MESSAGES
+#endif
+
+#if CONFIG_JFFS2_FS_DEBUG > 1
+#define JFFS2_DBG_FRAGTREE2_MESSAGES
+#define JFFS2_DBG_READINODE2_MESSAGES
+#define JFFS2_DBG_MEMALLOC_MESSAGES
+#endif
+
+/* Sanity checks are supposed to be light-weight and enabled by default */
+#define JFFS2_DBG_SANITY_CHECKS
+
+/*
+ * Dx() are mainly used for debugging messages, they must go away and be
+ * superseded by nicer dbg_xxx() macros...
+ */
+#if CONFIG_JFFS2_FS_DEBUG > 0
+#define DEBUG
+#define D1(x) x
+#else
+#define D1(x)
+#endif
+
+#if CONFIG_JFFS2_FS_DEBUG > 1
+#define D2(x) x
+#else
+#define D2(x)
+#endif
+
+#define jffs2_dbg(level, fmt, ...)		\
+do {						\
+	if (CONFIG_JFFS2_FS_DEBUG >= level)	\
+		pr_debug(fmt, ##__VA_ARGS__);	\
+} while (0)
+
+/* The prefixes of JFFS2 messages */
+#define JFFS2_DBG		KERN_DEBUG
+#define JFFS2_DBG_PREFIX	"[JFFS2 DBG]"
+#define JFFS2_DBG_MSG_PREFIX	JFFS2_DBG JFFS2_DBG_PREFIX
+
+/* JFFS2 message macros */
+#define JFFS2_ERROR(fmt, ...)					\
+	pr_err("error: (%d) %s: " fmt,				\
+	       task_pid_nr(current), __func__, ##__VA_ARGS__)
+
+#define JFFS2_WARNING(fmt, ...)						\
+	pr_warn("warning: (%d) %s: " fmt,				\
+		task_pid_nr(current), __func__, ##__VA_ARGS__)
+
+#define JFFS2_NOTICE(fmt, ...)						\
+	pr_notice("notice: (%d) %s: " fmt,				\
+		  task_pid_nr(current), __func__, ##__VA_ARGS__)
+
+#define JFFS2_DEBUG(fmt, ...)						\
+	printk(KERN_DEBUG "[JFFS2 DBG] (%d) %s: " fmt,			\
+	       task_pid_nr(current), __func__, ##__VA_ARGS__)
+
+/*
+ * We split our debugging messages on several parts, depending on the JFFS2
+ * subsystem the message belongs to.
+ */
+/* Read inode debugging messages */
+#ifdef JFFS2_DBG_READINODE_MESSAGES
+#define dbg_readinode(fmt, ...)	JFFS2_DEBUG(fmt, ##__VA_ARGS__)
+#else
+#define dbg_readinode(fmt, ...)	no_printk(fmt, ##__VA_ARGS__)
+#endif
+#ifdef JFFS2_DBG_READINODE2_MESSAGES
+#define dbg_readinode2(fmt, ...)	JFFS2_DEBUG(fmt, ##__VA_ARGS__)
+#else
+#define dbg_readinode2(fmt, ...)	no_printk(fmt, ##__VA_ARGS__)
+#endif
+
+/* Fragtree build debugging messages */
+#ifdef JFFS2_DBG_FRAGTREE_MESSAGES
+#define dbg_fragtree(fmt, ...)	JFFS2_DEBUG(fmt, ##__VA_ARGS__)
+#else
+#define dbg_fragtree(fmt, ...)	no_printk(fmt, ##__VA_ARGS__)
+#endif
+#ifdef JFFS2_DBG_FRAGTREE2_MESSAGES
+#define dbg_fragtree2(fmt, ...)	JFFS2_DEBUG(fmt, ##__VA_ARGS__)
+#else
+#define dbg_fragtree2(fmt, ...)	no_printk(fmt, ##__VA_ARGS__)
+#endif
+
+/* Directory entry list manilulation debugging messages */
+#ifdef JFFS2_DBG_DENTLIST_MESSAGES
+#define dbg_dentlist(fmt, ...)	JFFS2_DEBUG(fmt, ##__VA_ARGS__)
+#else
+#define dbg_dentlist(fmt, ...)	no_printk(fmt, ##__VA_ARGS__)
+#endif
+
+/* Print the messages about manipulating node_refs */
+#ifdef JFFS2_DBG_NODEREF_MESSAGES
+#define dbg_noderef(fmt, ...)	JFFS2_DEBUG(fmt, ##__VA_ARGS__)
+#else
+#define dbg_noderef(fmt, ...)	no_printk(fmt, ##__VA_ARGS__)
+#endif
+
+/* Manipulations with the list of inodes (JFFS2 inocache) */
+#ifdef JFFS2_DBG_INOCACHE_MESSAGES
+#define dbg_inocache(fmt, ...)	JFFS2_DEBUG(fmt, ##__VA_ARGS__)
+#else
+#define dbg_inocache(fmt, ...)	no_printk(fmt, ##__VA_ARGS__)
+#endif
+
+/* Summary debugging messages */
+#ifdef JFFS2_DBG_SUMMARY_MESSAGES
+#define dbg_summary(fmt, ...)	JFFS2_DEBUG(fmt, ##__VA_ARGS__)
+#else
+#define dbg_summary(fmt, ...)	no_printk(fmt, ##__VA_ARGS__)
+#endif
+
+/* File system build messages */
+#ifdef JFFS2_DBG_FSBUILD_MESSAGES
+#define dbg_fsbuild(fmt, ...)	JFFS2_DEBUG(fmt, ##__VA_ARGS__)
+#else
+#define dbg_fsbuild(fmt, ...)	no_printk(fmt, ##__VA_ARGS__)
+#endif
+
+/* Watch the object allocations */
+#ifdef JFFS2_DBG_MEMALLOC_MESSAGES
+#define dbg_memalloc(fmt, ...)	JFFS2_DEBUG(fmt, ##__VA_ARGS__)
+#else
+#define dbg_memalloc(fmt, ...)	no_printk(fmt, ##__VA_ARGS__)
+#endif
+
+/* Watch the XATTR subsystem */
+#ifdef JFFS2_DBG_XATTR_MESSAGES
+#define dbg_xattr(fmt, ...)  JFFS2_DEBUG(fmt, ##__VA_ARGS__)
+#else
+#define dbg_xattr(fmt, ...)  no_printk(fmt, ##__VA_ARGS__)
+#endif 
+
+/* "Sanity" checks */
+void
+__jffs2_dbg_acct_sanity_check_nolock(struct jffs2_sb_info *c,
+				     struct jffs2_eraseblock *jeb);
+void
+__jffs2_dbg_acct_sanity_check(struct jffs2_sb_info *c,
+			      struct jffs2_eraseblock *jeb);
+
+/* "Paranoia" checks */
+void
+__jffs2_dbg_fragtree_paranoia_check(struct jffs2_inode_info *f);
+void
+__jffs2_dbg_fragtree_paranoia_check_nolock(struct jffs2_inode_info *f);
+void
+__jffs2_dbg_acct_paranoia_check(struct jffs2_sb_info *c,
+			   	struct jffs2_eraseblock *jeb);
+void
+__jffs2_dbg_acct_paranoia_check_nolock(struct jffs2_sb_info *c,
+				       struct jffs2_eraseblock *jeb);
+void
+__jffs2_dbg_prewrite_paranoia_check(struct jffs2_sb_info *c,
+				    uint32_t ofs, int len);
+
+/* "Dump" functions */
+void
+__jffs2_dbg_dump_jeb(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb);
+void
+__jffs2_dbg_dump_jeb_nolock(struct jffs2_eraseblock *jeb);
+void
+__jffs2_dbg_dump_block_lists(struct jffs2_sb_info *c);
+void
+__jffs2_dbg_dump_block_lists_nolock(struct jffs2_sb_info *c);
+void
+__jffs2_dbg_dump_node_refs(struct jffs2_sb_info *c,
+		 	   struct jffs2_eraseblock *jeb);
+void
+__jffs2_dbg_dump_node_refs_nolock(struct jffs2_sb_info *c,
+				  struct jffs2_eraseblock *jeb);
+void
+__jffs2_dbg_dump_fragtree(struct jffs2_inode_info *f);
+void
+__jffs2_dbg_dump_fragtree_nolock(struct jffs2_inode_info *f);
+void
+__jffs2_dbg_dump_buffer(unsigned char *buf, int len, uint32_t offs);
+void
+__jffs2_dbg_dump_node(struct jffs2_sb_info *c, uint32_t ofs);
+
+#ifdef JFFS2_DBG_PARANOIA_CHECKS
+#define jffs2_dbg_fragtree_paranoia_check(f)			\
+	__jffs2_dbg_fragtree_paranoia_check(f)
+#define jffs2_dbg_fragtree_paranoia_check_nolock(f)		\
+	__jffs2_dbg_fragtree_paranoia_check_nolock(f)
+#define jffs2_dbg_acct_paranoia_check(c, jeb)			\
+	__jffs2_dbg_acct_paranoia_check(c,jeb)
+#define jffs2_dbg_acct_paranoia_check_nolock(c, jeb)		\
+	__jffs2_dbg_acct_paranoia_check_nolock(c,jeb)
+#define jffs2_dbg_prewrite_paranoia_check(c, ofs, len)		\
+	__jffs2_dbg_prewrite_paranoia_check(c, ofs, len)
+#else
+#define jffs2_dbg_fragtree_paranoia_check(f)
+#define jffs2_dbg_fragtree_paranoia_check_nolock(f)
+#define jffs2_dbg_acct_paranoia_check(c, jeb)
+#define jffs2_dbg_acct_paranoia_check_nolock(c, jeb)
+#define jffs2_dbg_prewrite_paranoia_check(c, ofs, len)
+#endif /* !JFFS2_PARANOIA_CHECKS */
+
+#ifdef JFFS2_DBG_DUMPS
+#define jffs2_dbg_dump_jeb(c, jeb)				\
+	__jffs2_dbg_dump_jeb(c, jeb);
+#define jffs2_dbg_dump_jeb_nolock(jeb)				\
+	__jffs2_dbg_dump_jeb_nolock(jeb);
+#define jffs2_dbg_dump_block_lists(c)				\
+	__jffs2_dbg_dump_block_lists(c)
+#define jffs2_dbg_dump_block_lists_nolock(c)			\
+	__jffs2_dbg_dump_block_lists_nolock(c)
+#define jffs2_dbg_dump_fragtree(f)				\
+	__jffs2_dbg_dump_fragtree(f);
+#define jffs2_dbg_dump_fragtree_nolock(f)			\
+	__jffs2_dbg_dump_fragtree_nolock(f);
+#define jffs2_dbg_dump_buffer(buf, len, offs)			\
+	__jffs2_dbg_dump_buffer(*buf, len, offs);
+#define jffs2_dbg_dump_node(c, ofs)				\
+	__jffs2_dbg_dump_node(c, ofs);
+#else
+#define jffs2_dbg_dump_jeb(c, jeb)
+#define jffs2_dbg_dump_jeb_nolock(jeb)
+#define jffs2_dbg_dump_block_lists(c)
+#define jffs2_dbg_dump_block_lists_nolock(c)
+#define jffs2_dbg_dump_fragtree(f)
+#define jffs2_dbg_dump_fragtree_nolock(f)
+#define jffs2_dbg_dump_buffer(buf, len, offs)
+#define jffs2_dbg_dump_node(c, ofs)
+#endif /* !JFFS2_DBG_DUMPS */
+
+#ifdef JFFS2_DBG_SANITY_CHECKS
+#define jffs2_dbg_acct_sanity_check(c, jeb)			\
+	__jffs2_dbg_acct_sanity_check(c, jeb)
+#define jffs2_dbg_acct_sanity_check_nolock(c, jeb)		\
+	__jffs2_dbg_acct_sanity_check_nolock(c, jeb)
+#else
+#define jffs2_dbg_acct_sanity_check(c, jeb)
+#define jffs2_dbg_acct_sanity_check_nolock(c, jeb)
+#endif /* !JFFS2_DBG_SANITY_CHECKS */
+
+#endif /* _JFFS2_DEBUG_H_ */