bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 74 insertions, 0 deletions

diff --git a/drivers/md/dm-pcache/segment.h b/drivers/md/dm-pcache/segment.h
new file mode 100644
index 000000000..deca1ddcb
--- /dev/null
+++ b/drivers/md/dm-pcache/segment.h
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _PCACHE_SEGMENT_H
+#define _PCACHE_SEGMENT_H
+
+#include <linux/bio.h>
+#include <linux/bitfield.h>
+
+#include "pcache_internal.h"
+
+struct pcache_segment_info {
+	struct pcache_meta_header	header;
+	__u32			flags;
+	__u32			next_seg;
+};
+
+#define PCACHE_SEG_INFO_FLAGS_HAS_NEXT		BIT(0)
+
+#define PCACHE_SEG_INFO_FLAGS_TYPE_MASK         GENMASK(4, 1)
+#define PCACHE_SEGMENT_TYPE_CACHE_DATA		1
+
+static inline bool segment_info_has_next(struct pcache_segment_info *seg_info)
+{
+	return (seg_info->flags & PCACHE_SEG_INFO_FLAGS_HAS_NEXT);
+}
+
+static inline void segment_info_set_type(struct pcache_segment_info *seg_info, u8 type)
+{
+	seg_info->flags &= ~PCACHE_SEG_INFO_FLAGS_TYPE_MASK;
+	seg_info->flags |= FIELD_PREP(PCACHE_SEG_INFO_FLAGS_TYPE_MASK, type);
+}
+
+static inline u8 segment_info_get_type(struct pcache_segment_info *seg_info)
+{
+	return FIELD_GET(PCACHE_SEG_INFO_FLAGS_TYPE_MASK, seg_info->flags);
+}
+
+struct pcache_segment_pos {
+	struct pcache_segment	*segment;	/* Segment associated with the position */
+	u32			off;		/* Offset within the segment */
+};
+
+struct pcache_segment_init_options {
+	u8			type;
+	u32			seg_id;
+	u32			data_off;
+
+	struct pcache_segment_info	*seg_info;
+};
+
+struct pcache_segment {
+	struct pcache_cache_dev	*cache_dev;
+
+	void			*data;
+	u32			data_size;
+	u32			seg_id;
+
+	struct pcache_segment_info	*seg_info;
+};
+
+int segment_copy_to_bio(struct pcache_segment *segment,
+		      u32 data_off, u32 data_len, struct bio *bio, u32 bio_off);
+int segment_copy_from_bio(struct pcache_segment *segment,
+			u32 data_off, u32 data_len, struct bio *bio, u32 bio_off);
+
+static inline void segment_pos_advance(struct pcache_segment_pos *seg_pos, u32 len)
+{
+	BUG_ON(seg_pos->off + len > seg_pos->segment->data_size);
+
+	seg_pos->off += len;
+}
+
+void pcache_segment_init(struct pcache_cache_dev *cache_dev, struct pcache_segment *segment,
+		      struct pcache_segment_init_options *options);
+#endif /* _PCACHE_SEGMENT_H */