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, 285 insertions, 0 deletions

diff --git a/fs/ocfs2/export.c b/fs/ocfs2/export.c
new file mode 100644
index 000000000..9c2665dd2
--- /dev/null
+++ b/fs/ocfs2/export.c
@@ -0,0 +1,285 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * export.c
+ *
+ * Functions to facilitate NFS exporting
+ *
+ * Copyright (C) 2002, 2005 Oracle.  All rights reserved.
+ */
+
+#include <linux/fs.h>
+#include <linux/types.h>
+
+#include <cluster/masklog.h>
+
+#include "ocfs2.h"
+
+#include "alloc.h"
+#include "dir.h"
+#include "dlmglue.h"
+#include "dcache.h"
+#include "export.h"
+#include "inode.h"
+
+#include "buffer_head_io.h"
+#include "suballoc.h"
+#include "ocfs2_trace.h"
+
+struct ocfs2_inode_handle
+{
+	u64 ih_blkno;
+	u32 ih_generation;
+};
+
+static struct dentry *ocfs2_get_dentry(struct super_block *sb,
+		struct ocfs2_inode_handle *handle)
+{
+	struct inode *inode;
+	struct ocfs2_super *osb = OCFS2_SB(sb);
+	u64 blkno = handle->ih_blkno;
+	int status, set;
+	struct dentry *result;
+
+	trace_ocfs2_get_dentry_begin(sb, handle, (unsigned long long)blkno);
+
+	if (blkno == 0) {
+		result = ERR_PTR(-ESTALE);
+		goto bail;
+	}
+
+	inode = ocfs2_ilookup(sb, blkno);
+	/*
+	 * If the inode exists in memory, we only need to check it's
+	 * generation number
+	 */
+	if (inode)
+		goto check_gen;
+
+	/*
+	 * This will synchronize us against ocfs2_delete_inode() on
+	 * all nodes
+	 */
+	status = ocfs2_nfs_sync_lock(osb, 1);
+	if (status < 0) {
+		mlog(ML_ERROR, "getting nfs sync lock(EX) failed %d\n", status);
+		goto check_err;
+	}
+
+	status = ocfs2_test_inode_bit(osb, blkno, &set);
+	if (status < 0) {
+		if (status == -EINVAL) {
+			/*
+			 * The blkno NFS gave us doesn't even show up
+			 * as an inode, we return -ESTALE to be
+			 * nice
+			 */
+			status = -ESTALE;
+		} else if (status != -ESTALE) {
+			mlog(ML_ERROR, "test inode bit failed %d\n", status);
+		}
+		goto unlock_nfs_sync;
+	}
+
+	trace_ocfs2_get_dentry_test_bit(status, set);
+	/* If the inode allocator bit is clear, this inode must be stale */
+	if (!set) {
+		status = -ESTALE;
+		goto unlock_nfs_sync;
+	}
+
+	inode = ocfs2_iget(osb, blkno, 0, 0);
+
+unlock_nfs_sync:
+	ocfs2_nfs_sync_unlock(osb, 1);
+
+check_err:
+	if (status < 0) {
+		if (status == -ESTALE) {
+			trace_ocfs2_get_dentry_stale((unsigned long long)blkno,
+						     handle->ih_generation);
+		}
+		result = ERR_PTR(status);
+		goto bail;
+	}
+
+	if (IS_ERR(inode)) {
+		mlog_errno(PTR_ERR(inode));
+		result = ERR_CAST(inode);
+		goto bail;
+	}
+
+check_gen:
+	if (handle->ih_generation != inode->i_generation) {
+		trace_ocfs2_get_dentry_generation((unsigned long long)blkno,
+						  handle->ih_generation,
+						  inode->i_generation);
+		iput(inode);
+		result = ERR_PTR(-ESTALE);
+		goto bail;
+	}
+
+	result = d_obtain_alias(inode);
+	if (IS_ERR(result))
+		mlog_errno(PTR_ERR(result));
+
+bail:
+	trace_ocfs2_get_dentry_end(result);
+	return result;
+}
+
+static struct dentry *ocfs2_get_parent(struct dentry *child)
+{
+	int status;
+	u64 blkno;
+	struct dentry *parent;
+	struct inode *dir = d_inode(child);
+	int set;
+
+	trace_ocfs2_get_parent(child, child->d_name.len, child->d_name.name,
+			       (unsigned long long)OCFS2_I(dir)->ip_blkno);
+
+	status = ocfs2_nfs_sync_lock(OCFS2_SB(dir->i_sb), 1);
+	if (status < 0) {
+		mlog(ML_ERROR, "getting nfs sync lock(EX) failed %d\n", status);
+		parent = ERR_PTR(status);
+		goto bail;
+	}
+
+	status = ocfs2_inode_lock(dir, NULL, 0);
+	if (status < 0) {
+		if (status != -ENOENT)
+			mlog_errno(status);
+		parent = ERR_PTR(status);
+		goto unlock_nfs_sync;
+	}
+
+	status = ocfs2_lookup_ino_from_name(dir, "..", 2, &blkno);
+	if (status < 0) {
+		parent = ERR_PTR(-ENOENT);
+		goto bail_unlock;
+	}
+
+	status = ocfs2_test_inode_bit(OCFS2_SB(dir->i_sb), blkno, &set);
+	if (status < 0) {
+		if (status == -EINVAL) {
+			status = -ESTALE;
+		} else if (status != -ESTALE) {
+			mlog(ML_ERROR, "test inode bit failed %d\n", status);
+		}
+		parent = ERR_PTR(status);
+		goto bail_unlock;
+	}
+
+	trace_ocfs2_get_dentry_test_bit(status, set);
+	if (!set) {
+		status = -ESTALE;
+		parent = ERR_PTR(status);
+		goto bail_unlock;
+	}
+
+	parent = d_obtain_alias(ocfs2_iget(OCFS2_SB(dir->i_sb), blkno, 0, 0));
+
+bail_unlock:
+	ocfs2_inode_unlock(dir, 0);
+
+unlock_nfs_sync:
+	ocfs2_nfs_sync_unlock(OCFS2_SB(dir->i_sb), 1);
+
+bail:
+	trace_ocfs2_get_parent_end(parent);
+
+	return parent;
+}
+
+static int ocfs2_encode_fh(struct inode *inode, u32 *fh_in, int *max_len,
+			   struct inode *parent)
+{
+	int len = *max_len;
+	int type = 1;
+	u64 blkno;
+	u32 generation;
+	__le32 *fh = (__force __le32 *) fh_in;
+
+#ifdef TRACE_HOOKS_ARE_NOT_BRAINDEAD_IN_YOUR_OPINION
+#error "You go ahead and fix that mess, then.  Somehow"
+	trace_ocfs2_encode_fh_begin(dentry, dentry->d_name.len,
+				    dentry->d_name.name,
+				    fh, len, connectable);
+#endif
+
+	if (parent && (len < 6)) {
+		*max_len = 6;
+		type = FILEID_INVALID;
+		goto bail;
+	} else if (len < 3) {
+		*max_len = 3;
+		type = FILEID_INVALID;
+		goto bail;
+	}
+
+	blkno = OCFS2_I(inode)->ip_blkno;
+	generation = inode->i_generation;
+
+	trace_ocfs2_encode_fh_self((unsigned long long)blkno, generation);
+
+	len = 3;
+	fh[0] = cpu_to_le32((u32)(blkno >> 32));
+	fh[1] = cpu_to_le32((u32)(blkno & 0xffffffff));
+	fh[2] = cpu_to_le32(generation);
+
+	if (parent) {
+		blkno = OCFS2_I(parent)->ip_blkno;
+		generation = parent->i_generation;
+
+		fh[3] = cpu_to_le32((u32)(blkno >> 32));
+		fh[4] = cpu_to_le32((u32)(blkno & 0xffffffff));
+		fh[5] = cpu_to_le32(generation);
+
+		len = 6;
+		type = 2;
+
+		trace_ocfs2_encode_fh_parent((unsigned long long)blkno,
+					     generation);
+	}
+
+	*max_len = len;
+
+bail:
+	trace_ocfs2_encode_fh_type(type);
+	return type;
+}
+
+static struct dentry *ocfs2_fh_to_dentry(struct super_block *sb,
+		struct fid *fid, int fh_len, int fh_type)
+{
+	struct ocfs2_inode_handle handle;
+
+	if (fh_len < 3 || fh_type > 2)
+		return NULL;
+
+	handle.ih_blkno = (u64)le32_to_cpu((__force __le32)fid->raw[0]) << 32;
+	handle.ih_blkno |= (u64)le32_to_cpu((__force __le32)fid->raw[1]);
+	handle.ih_generation = le32_to_cpu((__force __le32)fid->raw[2]);
+	return ocfs2_get_dentry(sb, &handle);
+}
+
+static struct dentry *ocfs2_fh_to_parent(struct super_block *sb,
+		struct fid *fid, int fh_len, int fh_type)
+{
+	struct ocfs2_inode_handle parent;
+
+	if (fh_type != 2 || fh_len < 6)
+		return NULL;
+
+	parent.ih_blkno = (u64)le32_to_cpu((__force __le32)fid->raw[3]) << 32;
+	parent.ih_blkno |= (u64)le32_to_cpu((__force __le32)fid->raw[4]);
+	parent.ih_generation = le32_to_cpu((__force __le32)fid->raw[5]);
+	return ocfs2_get_dentry(sb, &parent);
+}
+
+const struct export_operations ocfs2_export_ops = {
+	.encode_fh	= ocfs2_encode_fh,
+	.fh_to_dentry	= ocfs2_fh_to_dentry,
+	.fh_to_parent	= ocfs2_fh_to_parent,
+	.get_parent	= ocfs2_get_parent,
+};