bcachefs: Guard against unknown compression options

Since compression options now include compression level, proper
validation is a bit more involved.

This adds bch2_compression_opt_valid(), and plumbs it around
appropriately.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/compress.c

@@ -708,3 +708,13 @@ void bch2_opt_compression_to_text(struct printbuf *out,
 	if (opt.level)
 		prt_printf(out, ":%u", opt.level);
 }
+
+int bch2_opt_compression_validate(u64 v, struct printbuf *err)
+{
+	if (!bch2_compression_opt_valid(v)) {
+		prt_printf(err, "invalid compression opt %llu", v);
+		return -BCH_ERR_invalid_sb_opt_compression;
+	}
+
+	return 0;
+}

fs/bcachefs/compress.h

@@ -4,12 +4,18 @@
 
 #include "extents_types.h"
 
+static const unsigned __bch2_compression_opt_to_type[] = {
+#define x(t, n) [BCH_COMPRESSION_OPT_##t] = BCH_COMPRESSION_TYPE_##t,
+	BCH_COMPRESSION_OPTS()
+#undef x
+};
+
 struct bch_compression_opt {
 	u8		type:4,
 			level:4;
 };
 
-static inline struct bch_compression_opt bch2_compression_decode(unsigned v)
+static inline struct bch_compression_opt __bch2_compression_decode(unsigned v)
 {
 	return (struct bch_compression_opt) {
 		.type	= v & 15,
@@ -17,17 +23,25 @@ static inline struct bch_compression_opt bch2_compression_decode(unsigned v)
 	};
 }
 
+static inline bool bch2_compression_opt_valid(unsigned v)
+{
+	struct bch_compression_opt opt = __bch2_compression_decode(v);
+
+	return opt.type < ARRAY_SIZE(__bch2_compression_opt_to_type) && !(!opt.type && opt.level);
+}
+
+static inline struct bch_compression_opt bch2_compression_decode(unsigned v)
+{
+	return bch2_compression_opt_valid(v)
+		? __bch2_compression_decode(v)
+		: (struct bch_compression_opt) { 0 };
+}
+
 static inline unsigned bch2_compression_encode(struct bch_compression_opt opt)
 {
 	return opt.type|(opt.level << 4);
 }
 
-static const unsigned __bch2_compression_opt_to_type[] = {
-#define x(t, n) [BCH_COMPRESSION_OPT_##t] = BCH_COMPRESSION_TYPE_##t,
-	BCH_COMPRESSION_OPTS()
-#undef x
-};
-
 static inline enum bch_compression_type bch2_compression_opt_to_type(unsigned v)
 {
 	return __bch2_compression_opt_to_type[bch2_compression_decode(v).type];
@@ -46,10 +60,12 @@ int bch2_fs_compress_init(struct bch_fs *);
 
 int bch2_opt_compression_parse(struct bch_fs *, const char *, u64 *, struct printbuf *);
 void bch2_opt_compression_to_text(struct printbuf *, struct bch_fs *, struct bch_sb *, u64);
+int bch2_opt_compression_validate(u64, struct printbuf *);
 
 #define bch2_opt_compression (struct bch_opt_fn) {		\
-	.parse		= bch2_opt_compression_parse,	\
-	.to_text	= bch2_opt_compression_to_text,	\
+	.parse		= bch2_opt_compression_parse,		\
+	.to_text	= bch2_opt_compression_to_text,		\
+	.validate	= bch2_opt_compression_validate,	\
 }
 
 #endif /* _BCACHEFS_COMPRESS_H */

fs/bcachefs/errcode.h

@@ -213,6 +213,7 @@
 	x(BCH_ERR_invalid_sb,		invalid_sb_crypt)			\
 	x(BCH_ERR_invalid_sb,		invalid_sb_clean)			\
 	x(BCH_ERR_invalid_sb,		invalid_sb_quota)			\
+	x(BCH_ERR_invalid_sb,		invalid_sb_opt_compression)		\
 	x(BCH_ERR_invalid,		invalid_bkey)				\
 	x(BCH_ERR_operation_blocked,    nocow_lock_blocked)			\
 	x(EIO,				btree_node_read_err)			\

fs/bcachefs/inode.c

@@ -6,6 +6,7 @@
 #include "bkey_methods.h"
 #include "btree_update.h"
 #include "buckets.h"
+#include "compress.h"
 #include "error.h"
 #include "extents.h"
 #include "extent_update.h"
@@ -422,9 +423,10 @@ static int __bch2_inode_invalid(struct bkey_s_c k, struct printbuf *err)
 		return -BCH_ERR_invalid_bkey;
 	}
 
-	if (unpacked.bi_compression >= BCH_COMPRESSION_OPT_NR + 1) {
-		prt_printf(err, "invalid data checksum type (%u >= %u)",
-		       unpacked.bi_compression, BCH_COMPRESSION_OPT_NR + 1);
+	if (unpacked.bi_compression &&
+	    !bch2_compression_opt_valid(unpacked.bi_compression - 1)) {
+		prt_printf(err, "invalid compression opt %u",
+			   unpacked.bi_compression - 1);
 		return -BCH_ERR_invalid_bkey;
 	}
 

fs/bcachefs/opts.c

@@ -294,6 +294,9 @@ int bch2_opt_validate(const struct bch_option *opt, u64 v, struct printbuf *err)
 		return -EINVAL;
 	}
 
+	if (opt->fn.validate)
+		return opt->fn.validate(v, err);
+
 	return 0;
 }
 

fs/bcachefs/opts.h

@@ -74,6 +74,7 @@ enum opt_type {
 struct bch_opt_fn {
 	int (*parse)(struct bch_fs *, const char *, u64 *, struct printbuf *);
 	void (*to_text)(struct printbuf *, struct bch_fs *, struct bch_sb *, u64);
+	int (*validate)(u64, struct printbuf *);
 };
 
 /**