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, 438 insertions, 0 deletions

diff --git a/fs/ceph/ioctl.c b/fs/ceph/ioctl.c
new file mode 100644
index 000000000..12cb50e0a
--- /dev/null
+++ b/fs/ceph/ioctl.c
@@ -0,0 +1,438 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/ceph/ceph_debug.h>
+#include <linux/in.h>
+
+#include "super.h"
+#include "mds_client.h"
+#include "ioctl.h"
+#include <linux/ceph/striper.h>
+#include <linux/fscrypt.h>
+
+/*
+ * ioctls
+ */
+
+/*
+ * get and set the file layout
+ */
+static long ceph_ioctl_get_layout(struct file *file, void __user *arg)
+{
+	struct ceph_inode_info *ci = ceph_inode(file_inode(file));
+	struct ceph_ioctl_layout l;
+	int err;
+
+	err = ceph_do_getattr(file_inode(file), CEPH_STAT_CAP_LAYOUT, false);
+	if (!err) {
+		l.stripe_unit = ci->i_layout.stripe_unit;
+		l.stripe_count = ci->i_layout.stripe_count;
+		l.object_size = ci->i_layout.object_size;
+		l.data_pool = ci->i_layout.pool_id;
+		l.preferred_osd = -1;
+		if (copy_to_user(arg, &l, sizeof(l)))
+			return -EFAULT;
+	}
+
+	return err;
+}
+
+static long __validate_layout(struct ceph_mds_client *mdsc,
+			      struct ceph_ioctl_layout *l)
+{
+	int i, err;
+
+	/* validate striping parameters */
+	if ((l->object_size & ~PAGE_MASK) ||
+	    (l->stripe_unit & ~PAGE_MASK) ||
+	    ((unsigned)l->stripe_unit != 0 &&
+	     ((unsigned)l->object_size % (unsigned)l->stripe_unit)))
+		return -EINVAL;
+
+	/* make sure it's a valid data pool */
+	mutex_lock(&mdsc->mutex);
+	err = -EINVAL;
+	for (i = 0; i < mdsc->mdsmap->m_num_data_pg_pools; i++)
+		if (mdsc->mdsmap->m_data_pg_pools[i] == l->data_pool) {
+			err = 0;
+			break;
+		}
+	mutex_unlock(&mdsc->mutex);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static long ceph_ioctl_set_layout(struct file *file, void __user *arg)
+{
+	struct inode *inode = file_inode(file);
+	struct ceph_mds_client *mdsc = ceph_sb_to_fs_client(inode->i_sb)->mdsc;
+	struct ceph_mds_request *req;
+	struct ceph_ioctl_layout l;
+	struct ceph_inode_info *ci = ceph_inode(file_inode(file));
+	struct ceph_ioctl_layout nl;
+	int err;
+
+	if (!inode_owner_or_capable(file_mnt_idmap(file), inode))
+		return -EACCES;
+
+	if (copy_from_user(&l, arg, sizeof(l)))
+		return -EFAULT;
+
+	/* validate changed params against current layout */
+	err = ceph_do_getattr(file_inode(file), CEPH_STAT_CAP_LAYOUT, false);
+	if (err)
+		return err;
+
+	memset(&nl, 0, sizeof(nl));
+	if (l.stripe_count)
+		nl.stripe_count = l.stripe_count;
+	else
+		nl.stripe_count = ci->i_layout.stripe_count;
+	if (l.stripe_unit)
+		nl.stripe_unit = l.stripe_unit;
+	else
+		nl.stripe_unit = ci->i_layout.stripe_unit;
+	if (l.object_size)
+		nl.object_size = l.object_size;
+	else
+		nl.object_size = ci->i_layout.object_size;
+	if (l.data_pool)
+		nl.data_pool = l.data_pool;
+	else
+		nl.data_pool = ci->i_layout.pool_id;
+
+	/* this is obsolete, and always -1 */
+	nl.preferred_osd = -1;
+
+	err = __validate_layout(mdsc, &nl);
+	if (err)
+		return err;
+
+	req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_SETLAYOUT,
+				       USE_AUTH_MDS);
+	if (IS_ERR(req))
+		return PTR_ERR(req);
+	req->r_inode = inode;
+	ihold(inode);
+	req->r_num_caps = 1;
+
+	req->r_inode_drop = CEPH_CAP_FILE_SHARED | CEPH_CAP_FILE_EXCL;
+
+	req->r_args.setlayout.layout.fl_stripe_unit =
+		cpu_to_le32(l.stripe_unit);
+	req->r_args.setlayout.layout.fl_stripe_count =
+		cpu_to_le32(l.stripe_count);
+	req->r_args.setlayout.layout.fl_object_size =
+		cpu_to_le32(l.object_size);
+	req->r_args.setlayout.layout.fl_pg_pool = cpu_to_le32(l.data_pool);
+
+	err = ceph_mdsc_do_request(mdsc, NULL, req);
+	ceph_mdsc_put_request(req);
+	return err;
+}
+
+/*
+ * Set a layout policy on a directory inode. All items in the tree
+ * rooted at this inode will inherit this layout on creation,
+ * (It doesn't apply retroactively )
+ * unless a subdirectory has its own layout policy.
+ */
+static long ceph_ioctl_set_layout_policy (struct file *file, void __user *arg)
+{
+	struct inode *inode = file_inode(file);
+	struct ceph_mds_request *req;
+	struct ceph_ioctl_layout l;
+	int err;
+	struct ceph_mds_client *mdsc = ceph_sb_to_fs_client(inode->i_sb)->mdsc;
+
+	if (!inode_owner_or_capable(file_mnt_idmap(file), inode))
+		return -EACCES;
+
+	/* copy and validate */
+	if (copy_from_user(&l, arg, sizeof(l)))
+		return -EFAULT;
+
+	err = __validate_layout(mdsc, &l);
+	if (err)
+		return err;
+
+	req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_SETDIRLAYOUT,
+				       USE_AUTH_MDS);
+
+	if (IS_ERR(req))
+		return PTR_ERR(req);
+	req->r_inode = inode;
+	ihold(inode);
+	req->r_num_caps = 1;
+
+	req->r_args.setlayout.layout.fl_stripe_unit =
+			cpu_to_le32(l.stripe_unit);
+	req->r_args.setlayout.layout.fl_stripe_count =
+			cpu_to_le32(l.stripe_count);
+	req->r_args.setlayout.layout.fl_object_size =
+			cpu_to_le32(l.object_size);
+	req->r_args.setlayout.layout.fl_pg_pool =
+			cpu_to_le32(l.data_pool);
+
+	err = ceph_mdsc_do_request(mdsc, inode, req);
+	ceph_mdsc_put_request(req);
+	return err;
+}
+
+/*
+ * Return object name, size/offset information, and location (OSD
+ * number, network address) for a given file offset.
+ */
+static long ceph_ioctl_get_dataloc(struct file *file, void __user *arg)
+{
+	struct ceph_ioctl_dataloc dl;
+	struct inode *inode = file_inode(file);
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_osd_client *osdc =
+		&ceph_sb_to_fs_client(inode->i_sb)->client->osdc;
+	struct ceph_object_locator oloc;
+	CEPH_DEFINE_OID_ONSTACK(oid);
+	u32 xlen;
+	u64 tmp;
+	struct ceph_pg pgid;
+	int r;
+
+	/* copy and validate */
+	if (copy_from_user(&dl, arg, sizeof(dl)))
+		return -EFAULT;
+
+	down_read(&osdc->lock);
+	ceph_calc_file_object_mapping(&ci->i_layout, dl.file_offset, 1,
+				      &dl.object_no, &dl.object_offset, &xlen);
+	dl.file_offset -= dl.object_offset;
+	dl.object_size = ci->i_layout.object_size;
+	dl.block_size = ci->i_layout.stripe_unit;
+
+	/* block_offset = object_offset % block_size */
+	tmp = dl.object_offset;
+	dl.block_offset = do_div(tmp, dl.block_size);
+
+	snprintf(dl.object_name, sizeof(dl.object_name), "%llx.%08llx",
+		 ceph_ino(inode), dl.object_no);
+
+	oloc.pool = ci->i_layout.pool_id;
+	oloc.pool_ns = ceph_try_get_string(ci->i_layout.pool_ns);
+	ceph_oid_printf(&oid, "%s", dl.object_name);
+
+	r = ceph_object_locator_to_pg(osdc->osdmap, &oid, &oloc, &pgid);
+
+	ceph_oloc_destroy(&oloc);
+	if (r < 0) {
+		up_read(&osdc->lock);
+		return r;
+	}
+
+	dl.osd = ceph_pg_to_acting_primary(osdc->osdmap, &pgid);
+	if (dl.osd >= 0) {
+		struct ceph_entity_addr *a =
+			ceph_osd_addr(osdc->osdmap, dl.osd);
+		if (a)
+			memcpy(&dl.osd_addr, &a->in_addr, sizeof(dl.osd_addr));
+	} else {
+		memset(&dl.osd_addr, 0, sizeof(dl.osd_addr));
+	}
+	up_read(&osdc->lock);
+
+	/* send result back to user */
+	if (copy_to_user(arg, &dl, sizeof(dl)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static long ceph_ioctl_lazyio(struct file *file)
+{
+	struct ceph_file_info *fi = file->private_data;
+	struct inode *inode = file_inode(file);
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_mds_client *mdsc = ceph_inode_to_fs_client(inode)->mdsc;
+	struct ceph_client *cl = mdsc->fsc->client;
+	bool is_file_already_lazy = false;
+
+	spin_lock(&ci->i_ceph_lock);
+	if ((fi->fmode & CEPH_FILE_MODE_LAZY) == 0) {
+		fi->fmode |= CEPH_FILE_MODE_LAZY;
+		ci->i_nr_by_mode[ffs(CEPH_FILE_MODE_LAZY)]++;
+		__ceph_touch_fmode(ci, mdsc, fi->fmode);
+	} else {
+		is_file_already_lazy = true;
+	}
+	spin_unlock(&ci->i_ceph_lock);
+
+	if (is_file_already_lazy) {
+		doutc(cl, "file %p %p %llx.%llx already lazy\n", file, inode,
+		      ceph_vinop(inode));
+	} else {
+		doutc(cl, "file %p %p %llx.%llx marked lazy\n", file, inode,
+		      ceph_vinop(inode));
+
+		ceph_check_caps(ci, 0);
+	}
+
+	return 0;
+}
+
+static long ceph_ioctl_syncio(struct file *file)
+{
+	struct ceph_file_info *fi = file->private_data;
+
+	fi->flags |= CEPH_F_SYNC;
+	return 0;
+}
+
+static int vet_mds_for_fscrypt(struct file *file)
+{
+	int i, ret = -EOPNOTSUPP;
+	struct ceph_mds_client	*mdsc = ceph_sb_to_mdsc(file_inode(file)->i_sb);
+
+	mutex_lock(&mdsc->mutex);
+	for (i = 0; i < mdsc->max_sessions; i++) {
+		struct ceph_mds_session *s = mdsc->sessions[i];
+
+		if (!s)
+			continue;
+		if (test_bit(CEPHFS_FEATURE_ALTERNATE_NAME, &s->s_features))
+			ret = 0;
+		break;
+	}
+	mutex_unlock(&mdsc->mutex);
+	return ret;
+}
+
+static long ceph_set_encryption_policy(struct file *file, unsigned long arg)
+{
+	int ret, got = 0;
+	struct inode *inode = file_inode(file);
+	struct ceph_inode_info *ci = ceph_inode(inode);
+
+	/* encrypted directories can't have striped layout */
+	if (ci->i_layout.stripe_count > 1)
+		return -EINVAL;
+
+	ret = vet_mds_for_fscrypt(file);
+	if (ret)
+		return ret;
+
+	/*
+	 * Ensure we hold these caps so that we _know_ that the rstats check
+	 * in the empty_dir check is reliable.
+	 */
+	ret = ceph_get_caps(file, CEPH_CAP_FILE_SHARED, 0, -1, &got);
+	if (ret)
+		return ret;
+
+	ret = fscrypt_ioctl_set_policy(file, (const void __user *)arg);
+	if (got)
+		ceph_put_cap_refs(ci, got);
+
+	return ret;
+}
+
+static const char *ceph_ioctl_cmd_name(const unsigned int cmd)
+{
+	switch (cmd) {
+	case CEPH_IOC_GET_LAYOUT:
+		return "get_layout";
+	case CEPH_IOC_SET_LAYOUT:
+		return "set_layout";
+	case CEPH_IOC_SET_LAYOUT_POLICY:
+		return "set_layout_policy";
+	case CEPH_IOC_GET_DATALOC:
+		return "get_dataloc";
+	case CEPH_IOC_LAZYIO:
+		return "lazyio";
+	case CEPH_IOC_SYNCIO:
+		return "syncio";
+	case FS_IOC_SET_ENCRYPTION_POLICY:
+		return "set_encryption_policy";
+	case FS_IOC_GET_ENCRYPTION_POLICY:
+		return "get_encryption_policy";
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+		return "get_encryption_policy_ex";
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+		return "add_encryption_key";
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+		return "remove_encryption_key";
+	case FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS:
+		return "remove_encryption_key_all_users";
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
+		return "get_encryption_key_status";
+	case FS_IOC_GET_ENCRYPTION_NONCE:
+		return "get_encryption_nonce";
+	default:
+		return "unknown";
+	}
+}
+
+long ceph_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct inode *inode = file_inode(file);
+	struct ceph_fs_client *fsc = ceph_inode_to_fs_client(inode);
+	int ret;
+
+	doutc(fsc->client, "file %p %p %llx.%llx cmd %s arg %lu\n", file,
+	      inode, ceph_vinop(inode), ceph_ioctl_cmd_name(cmd), arg);
+	switch (cmd) {
+	case CEPH_IOC_GET_LAYOUT:
+		return ceph_ioctl_get_layout(file, (void __user *)arg);
+
+	case CEPH_IOC_SET_LAYOUT:
+		return ceph_ioctl_set_layout(file, (void __user *)arg);
+
+	case CEPH_IOC_SET_LAYOUT_POLICY:
+		return ceph_ioctl_set_layout_policy(file, (void __user *)arg);
+
+	case CEPH_IOC_GET_DATALOC:
+		return ceph_ioctl_get_dataloc(file, (void __user *)arg);
+
+	case CEPH_IOC_LAZYIO:
+		return ceph_ioctl_lazyio(file);
+
+	case CEPH_IOC_SYNCIO:
+		return ceph_ioctl_syncio(file);
+
+	case FS_IOC_SET_ENCRYPTION_POLICY:
+		return ceph_set_encryption_policy(file, arg);
+
+	case FS_IOC_GET_ENCRYPTION_POLICY:
+		ret = vet_mds_for_fscrypt(file);
+		if (ret)
+			return ret;
+		return fscrypt_ioctl_get_policy(file, (void __user *)arg);
+
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+		ret = vet_mds_for_fscrypt(file);
+		if (ret)
+			return ret;
+		return fscrypt_ioctl_get_policy_ex(file, (void __user *)arg);
+
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+		ret = vet_mds_for_fscrypt(file);
+		if (ret)
+			return ret;
+		return fscrypt_ioctl_add_key(file, (void __user *)arg);
+
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+		return fscrypt_ioctl_remove_key(file, (void __user *)arg);
+
+	case FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS:
+		return fscrypt_ioctl_remove_key_all_users(file,
+							  (void __user *)arg);
+
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
+		return fscrypt_ioctl_get_key_status(file, (void __user *)arg);
+
+	case FS_IOC_GET_ENCRYPTION_NONCE:
+		ret = vet_mds_for_fscrypt(file);
+		if (ret)
+			return ret;
+		return fscrypt_ioctl_get_nonce(file, (void __user *)arg);
+	}
+
+	return -ENOTTY;
+}