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, 478 insertions, 0 deletions

diff --git a/drivers/md/dm-pcache/cache.c b/drivers/md/dm-pcache/cache.c
new file mode 100644
index 000000000..b0b3e2167
--- /dev/null
+++ b/drivers/md/dm-pcache/cache.c
@@ -0,0 +1,478 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/blk_types.h>
+
+#include "cache.h"
+#include "cache_dev.h"
+#include "backing_dev.h"
+#include "dm_pcache.h"
+
+struct kmem_cache *key_cache;
+
+static inline struct pcache_cache_info *get_cache_info_addr(struct pcache_cache *cache)
+{
+	return (struct pcache_cache_info *)((char *)cache->cache_info_addr +
+						(size_t)cache->info_index * PCACHE_CACHE_INFO_SIZE);
+}
+
+static void cache_info_write(struct pcache_cache *cache)
+{
+	struct pcache_cache_info *cache_info = &cache->cache_info;
+
+	cache_info->header.seq++;
+	cache_info->header.crc = pcache_meta_crc(&cache_info->header,
+						sizeof(struct pcache_cache_info));
+
+	cache->info_index = (cache->info_index + 1) % PCACHE_META_INDEX_MAX;
+	memcpy_flushcache(get_cache_info_addr(cache), cache_info,
+			sizeof(struct pcache_cache_info));
+	pmem_wmb();
+}
+
+static void cache_info_init_default(struct pcache_cache *cache);
+static int cache_info_init(struct pcache_cache *cache, struct pcache_cache_options *opts)
+{
+	struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
+	struct pcache_cache_info *cache_info_addr;
+
+	cache_info_addr = pcache_meta_find_latest(&cache->cache_info_addr->header,
+						sizeof(struct pcache_cache_info),
+						PCACHE_CACHE_INFO_SIZE,
+						&cache->cache_info);
+	if (IS_ERR(cache_info_addr))
+		return PTR_ERR(cache_info_addr);
+
+	if (cache_info_addr) {
+		if (opts->data_crc !=
+				(cache->cache_info.flags & PCACHE_CACHE_FLAGS_DATA_CRC)) {
+			pcache_dev_err(pcache, "invalid option for data_crc: %s, expected: %s",
+					opts->data_crc ? "true" : "false",
+					cache->cache_info.flags & PCACHE_CACHE_FLAGS_DATA_CRC ? "true" : "false");
+			return -EINVAL;
+		}
+
+		cache->info_index = ((char *)cache_info_addr - (char *)cache->cache_info_addr) / PCACHE_CACHE_INFO_SIZE;
+
+		return 0;
+	}
+
+	/* init cache_info for new cache */
+	cache_info_init_default(cache);
+	cache_mode_set(cache, opts->cache_mode);
+	if (opts->data_crc)
+		cache->cache_info.flags |= PCACHE_CACHE_FLAGS_DATA_CRC;
+
+	return 0;
+}
+
+static void cache_info_set_gc_percent(struct pcache_cache_info *cache_info, u8 percent)
+{
+	cache_info->flags &= ~PCACHE_CACHE_FLAGS_GC_PERCENT_MASK;
+	cache_info->flags |= FIELD_PREP(PCACHE_CACHE_FLAGS_GC_PERCENT_MASK, percent);
+}
+
+int pcache_cache_set_gc_percent(struct pcache_cache *cache, u8 percent)
+{
+	if (percent > PCACHE_CACHE_GC_PERCENT_MAX || percent < PCACHE_CACHE_GC_PERCENT_MIN)
+		return -EINVAL;
+
+	mutex_lock(&cache->cache_info_lock);
+	cache_info_set_gc_percent(&cache->cache_info, percent);
+
+	cache_info_write(cache);
+	mutex_unlock(&cache->cache_info_lock);
+
+	return 0;
+}
+
+void cache_pos_encode(struct pcache_cache *cache,
+			     struct pcache_cache_pos_onmedia *pos_onmedia_base,
+			     struct pcache_cache_pos *pos, u64 seq, u32 *index)
+{
+	struct pcache_cache_pos_onmedia pos_onmedia;
+	struct pcache_cache_pos_onmedia *pos_onmedia_addr = pos_onmedia_base + *index;
+
+	pos_onmedia.cache_seg_id = pos->cache_seg->cache_seg_id;
+	pos_onmedia.seg_off = pos->seg_off;
+	pos_onmedia.header.seq = seq;
+	pos_onmedia.header.crc = cache_pos_onmedia_crc(&pos_onmedia);
+
+	*index = (*index + 1) % PCACHE_META_INDEX_MAX;
+
+	memcpy_flushcache(pos_onmedia_addr, &pos_onmedia, sizeof(struct pcache_cache_pos_onmedia));
+	pmem_wmb();
+}
+
+int cache_pos_decode(struct pcache_cache *cache,
+			    struct pcache_cache_pos_onmedia *pos_onmedia,
+			    struct pcache_cache_pos *pos, u64 *seq, u32 *index)
+{
+	struct pcache_cache_pos_onmedia latest, *latest_addr;
+
+	latest_addr = pcache_meta_find_latest(&pos_onmedia->header,
+					sizeof(struct pcache_cache_pos_onmedia),
+					sizeof(struct pcache_cache_pos_onmedia),
+					&latest);
+	if (IS_ERR(latest_addr))
+		return PTR_ERR(latest_addr);
+
+	if (!latest_addr)
+		return -EIO;
+
+	if (!cache_seg_id_valid(cache, latest.cache_seg_id))
+		return -EIO;
+
+	pos->cache_seg = &cache->segments[latest.cache_seg_id];
+
+	if (latest.seg_off >= pos->cache_seg->segment.data_size)
+		return -EIO;
+
+	pos->seg_off = latest.seg_off;
+	*seq = latest.header.seq;
+	*index = (latest_addr - pos_onmedia);
+
+	return 0;
+}
+
+static inline void cache_info_set_seg_id(struct pcache_cache *cache, u32 seg_id)
+{
+	cache->cache_info.seg_id = seg_id;
+}
+
+static int cache_init(struct dm_pcache *pcache)
+{
+	struct pcache_cache *cache = &pcache->cache;
+	struct pcache_backing_dev *backing_dev = &pcache->backing_dev;
+	struct pcache_cache_dev *cache_dev = &pcache->cache_dev;
+	int ret;
+
+	cache->segments = kvzalloc_objs(struct pcache_cache_segment,
+					cache_dev->seg_num);
+	if (!cache->segments) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	cache->seg_map = kvcalloc(BITS_TO_LONGS(cache_dev->seg_num), sizeof(unsigned long), GFP_KERNEL);
+	if (!cache->seg_map) {
+		ret = -ENOMEM;
+		goto free_segments;
+	}
+
+	cache->backing_dev = backing_dev;
+	cache->cache_dev = &pcache->cache_dev;
+	cache->n_segs = cache_dev->seg_num;
+	atomic_set(&cache->gc_errors, 0);
+	atomic_set(&cache->writeback_errors, 0);
+	spin_lock_init(&cache->seg_map_lock);
+	spin_lock_init(&cache->key_head_lock);
+
+	mutex_init(&cache->cache_info_lock);
+	mutex_init(&cache->key_tail_lock);
+	mutex_init(&cache->dirty_tail_lock);
+	mutex_init(&cache->writeback_lock);
+
+	INIT_DELAYED_WORK(&cache->writeback_work, cache_writeback_fn);
+	INIT_DELAYED_WORK(&cache->gc_work, pcache_cache_gc_fn);
+	INIT_WORK(&cache->clean_work, clean_fn);
+
+	return 0;
+
+free_segments:
+	kvfree(cache->segments);
+err:
+	return ret;
+}
+
+static void cache_exit(struct pcache_cache *cache)
+{
+	kvfree(cache->seg_map);
+	kvfree(cache->segments);
+}
+
+static void cache_info_init_default(struct pcache_cache *cache)
+{
+	struct pcache_cache_info *cache_info = &cache->cache_info;
+
+	memset(cache_info, 0, sizeof(*cache_info));
+	cache_info->n_segs = cache->cache_dev->seg_num;
+	cache_info_set_gc_percent(cache_info, PCACHE_CACHE_GC_PERCENT_DEFAULT);
+}
+
+static int cache_tail_init(struct pcache_cache *cache)
+{
+	struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
+	bool new_cache = !(cache->cache_info.flags & PCACHE_CACHE_FLAGS_INIT_DONE);
+	int ret;
+
+	if (new_cache) {
+		__set_bit(0, cache->seg_map);
+
+		cache->key_head.cache_seg = &cache->segments[0];
+		cache->key_head.seg_off = 0;
+		cache_pos_copy(&cache->key_tail, &cache->key_head);
+		cache_pos_copy(&cache->dirty_tail, &cache->key_head);
+
+		cache_encode_dirty_tail(cache);
+		cache_encode_key_tail(cache);
+	} else {
+		if (cache_decode_key_tail(cache) || cache_decode_dirty_tail(cache)) {
+			pcache_dev_err(pcache, "Corrupted key tail or dirty tail.\n");
+			return -EIO;
+		}
+
+		ret = cache_verify_dirty_tail(cache);
+		if (ret) {
+			pcache_dev_err(pcache, "dirty tail chain does not terminate (crafted cache image?)\n");
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+static int get_seg_id(struct pcache_cache *cache,
+		      struct pcache_cache_segment *prev_cache_seg,
+		      bool new_cache, u32 *seg_id)
+{
+	struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
+	struct pcache_cache_dev *cache_dev = cache->cache_dev;
+	int ret;
+
+	if (new_cache) {
+		ret = cache_dev_get_empty_segment_id(cache_dev, seg_id);
+		if (ret) {
+			pcache_dev_err(pcache, "no available segment\n");
+			goto err;
+		}
+
+		if (prev_cache_seg)
+			cache_seg_set_next_seg(prev_cache_seg, *seg_id);
+		else
+			cache_info_set_seg_id(cache, *seg_id);
+	} else {
+		if (prev_cache_seg) {
+			struct pcache_segment_info *prev_seg_info;
+
+			prev_seg_info = &prev_cache_seg->cache_seg_info;
+			if (!segment_info_has_next(prev_seg_info)) {
+				ret = -EFAULT;
+				goto err;
+			}
+			*seg_id = prev_cache_seg->cache_seg_info.next_seg;
+		} else {
+			*seg_id = cache->cache_info.seg_id;
+		}
+
+		if (*seg_id >= cache_dev->seg_num) {
+			pcache_dev_err(pcache, "invalid segment id %u from cache device (seg_num %u)\n",
+				       *seg_id, cache_dev->seg_num);
+			ret = -EIO;
+			goto err;
+		}
+	}
+	return 0;
+err:
+	return ret;
+}
+
+static int cache_segs_init(struct pcache_cache *cache)
+{
+	struct pcache_cache_segment *prev_cache_seg = NULL;
+	struct pcache_cache_info *cache_info = &cache->cache_info;
+	bool new_cache = !(cache->cache_info.flags & PCACHE_CACHE_FLAGS_INIT_DONE);
+	u32 seg_id;
+	int ret;
+	u32 i;
+
+	if (cache_info->n_segs > cache->cache_dev->seg_num) {
+		pcache_dev_err(CACHE_TO_PCACHE(cache),
+			       "cache_info n_segs %u exceeds cache device segments %u\n",
+			       cache_info->n_segs, cache->cache_dev->seg_num);
+		return -EIO;
+	}
+
+	for (i = 0; i < cache_info->n_segs; i++) {
+		ret = get_seg_id(cache, prev_cache_seg, new_cache, &seg_id);
+		if (ret)
+			goto err;
+
+		ret = cache_seg_init(cache, seg_id, i, new_cache);
+		if (ret)
+			goto err;
+
+		prev_cache_seg = &cache->segments[i];
+	}
+	return 0;
+err:
+	return ret;
+}
+
+static int cache_init_req_keys(struct pcache_cache *cache, u32 n_paral)
+{
+	struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
+	u32 n_subtrees;
+	int ret;
+	u32 i, cpu;
+
+	/* Calculate number of cache trees based on the device size */
+	n_subtrees = DIV_ROUND_UP(cache->dev_size << SECTOR_SHIFT, PCACHE_CACHE_SUBTREE_SIZE);
+	ret = cache_tree_init(cache, &cache->req_key_tree, n_subtrees);
+	if (ret)
+		goto err;
+
+	cache->n_ksets = n_paral;
+	cache->ksets = kvcalloc(cache->n_ksets, PCACHE_KSET_SIZE, GFP_KERNEL);
+	if (!cache->ksets) {
+		ret = -ENOMEM;
+		goto req_tree_exit;
+	}
+
+	/*
+	 * Initialize each kset with a spinlock and delayed work for flushing.
+	 * Each kset is associated with one queue to ensure independent handling
+	 * of cache keys across multiple queues, maximizing multiqueue concurrency.
+	 */
+	for (i = 0; i < cache->n_ksets; i++) {
+		struct pcache_cache_kset *kset = get_kset(cache, i);
+
+		kset->cache = cache;
+		spin_lock_init(&kset->kset_lock);
+		INIT_DELAYED_WORK(&kset->flush_work, kset_flush_fn);
+	}
+
+	cache->data_heads = alloc_percpu(struct pcache_cache_data_head);
+	if (!cache->data_heads) {
+		ret = -ENOMEM;
+		goto free_kset;
+	}
+
+	for_each_possible_cpu(cpu) {
+		struct pcache_cache_data_head *h =
+			per_cpu_ptr(cache->data_heads, cpu);
+		h->head_pos.cache_seg = NULL;
+	}
+
+	/*
+	 * Replay persisted cache keys using cache_replay.
+	 * This function loads and replays cache keys from previously stored
+	 * ksets, allowing the cache to restore its state after a restart.
+	 */
+	ret = cache_replay(cache);
+	if (ret) {
+		pcache_dev_err(pcache, "failed to replay keys\n");
+		goto free_heads;
+	}
+
+	return 0;
+
+free_heads:
+	free_percpu(cache->data_heads);
+free_kset:
+	kvfree(cache->ksets);
+req_tree_exit:
+	cache_tree_exit(&cache->req_key_tree);
+err:
+	return ret;
+}
+
+static void cache_destroy_req_keys(struct pcache_cache *cache)
+{
+	u32 i;
+
+	for (i = 0; i < cache->n_ksets; i++) {
+		struct pcache_cache_kset *kset = get_kset(cache, i);
+
+		cancel_delayed_work_sync(&kset->flush_work);
+	}
+
+	free_percpu(cache->data_heads);
+	kvfree(cache->ksets);
+	cache_tree_exit(&cache->req_key_tree);
+}
+
+int pcache_cache_start(struct dm_pcache *pcache)
+{
+	struct pcache_backing_dev *backing_dev = &pcache->backing_dev;
+	struct pcache_cache *cache = &pcache->cache;
+	struct pcache_cache_options *opts = &pcache->opts;
+	int ret;
+
+	ret = cache_init(pcache);
+	if (ret)
+		return ret;
+
+	cache->cache_info_addr = CACHE_DEV_CACHE_INFO(cache->cache_dev);
+	cache->cache_ctrl = CACHE_DEV_CACHE_CTRL(cache->cache_dev);
+	backing_dev->cache = cache;
+	cache->dev_size = backing_dev->dev_size;
+
+	ret = cache_info_init(cache, opts);
+	if (ret)
+		goto cache_exit;
+
+	ret = cache_segs_init(cache);
+	if (ret)
+		goto cache_exit;
+
+	ret = cache_tail_init(cache);
+	if (ret)
+		goto cache_exit;
+
+	ret = cache_init_req_keys(cache, num_online_cpus());
+	if (ret)
+		goto cache_exit;
+
+	ret = cache_writeback_init(cache);
+	if (ret)
+		goto destroy_keys;
+
+	cache->cache_info.flags |= PCACHE_CACHE_FLAGS_INIT_DONE;
+	cache_info_write(cache);
+	queue_delayed_work(cache_get_wq(cache), &cache->gc_work, 0);
+
+	return 0;
+
+destroy_keys:
+	cache_destroy_req_keys(cache);
+cache_exit:
+	cache_exit(cache);
+
+	return ret;
+}
+
+void pcache_cache_stop(struct dm_pcache *pcache)
+{
+	struct pcache_cache *cache = &pcache->cache;
+
+	pcache_cache_flush(cache);
+
+	cancel_delayed_work_sync(&cache->gc_work);
+	flush_work(&cache->clean_work);
+	cache_writeback_exit(cache);
+
+	if (cache->req_key_tree.n_subtrees)
+		cache_destroy_req_keys(cache);
+
+	cache_exit(cache);
+}
+
+struct workqueue_struct *cache_get_wq(struct pcache_cache *cache)
+{
+	struct dm_pcache *pcache = CACHE_TO_PCACHE(cache);
+
+	return pcache->task_wq;
+}
+
+int pcache_cache_init(void)
+{
+	key_cache = KMEM_CACHE(pcache_cache_key, 0);
+	if (!key_cache)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void pcache_cache_exit(void)
+{
+	kmem_cache_destroy(key_cache);
+}