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f1a880a93b
If the hash tree itself is sufficiently corrupt in addition to data blocks,
it's possible for error correction to end up in a deep recursive loop,
which eventually causes a kernel panic. This change limits the
recursion to a reasonable level during a single I/O operation.
Fixes: a739ff3f54 ("dm verity: add support for forward error correction")
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # v4.5+
157 lines
4.4 KiB
C
157 lines
4.4 KiB
C
/*
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* Copyright (C) 2015 Google, Inc.
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*
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* Author: Sami Tolvanen <samitolvanen@google.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*/
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#ifndef DM_VERITY_FEC_H
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#define DM_VERITY_FEC_H
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#include "dm-verity.h"
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#include <linux/rslib.h>
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/* Reed-Solomon(M, N) parameters */
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#define DM_VERITY_FEC_RSM 255
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#define DM_VERITY_FEC_MAX_RSN 253
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#define DM_VERITY_FEC_MIN_RSN 231 /* ~10% space overhead */
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/* buffers for deinterleaving and decoding */
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#define DM_VERITY_FEC_BUF_PREALLOC 1 /* buffers to preallocate */
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#define DM_VERITY_FEC_BUF_RS_BITS 4 /* 1 << RS blocks per buffer */
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/* we need buffers for at most 1 << block size RS blocks */
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#define DM_VERITY_FEC_BUF_MAX \
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(1 << (PAGE_SHIFT - DM_VERITY_FEC_BUF_RS_BITS))
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/* maximum recursion level for verity_fec_decode */
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#define DM_VERITY_FEC_MAX_RECURSION 4
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#define DM_VERITY_OPT_FEC_DEV "use_fec_from_device"
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#define DM_VERITY_OPT_FEC_BLOCKS "fec_blocks"
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#define DM_VERITY_OPT_FEC_START "fec_start"
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#define DM_VERITY_OPT_FEC_ROOTS "fec_roots"
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/* configuration */
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struct dm_verity_fec {
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struct dm_dev *dev; /* parity data device */
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struct dm_bufio_client *data_bufio; /* for data dev access */
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struct dm_bufio_client *bufio; /* for parity data access */
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sector_t start; /* parity data start in blocks */
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sector_t blocks; /* number of blocks covered */
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sector_t rounds; /* number of interleaving rounds */
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sector_t hash_blocks; /* blocks covered after v->hash_start */
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unsigned char roots; /* number of parity bytes, M-N of RS(M, N) */
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unsigned char rsn; /* N of RS(M, N) */
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mempool_t *rs_pool; /* mempool for fio->rs */
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mempool_t *prealloc_pool; /* mempool for preallocated buffers */
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mempool_t *extra_pool; /* mempool for extra buffers */
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mempool_t *output_pool; /* mempool for output */
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struct kmem_cache *cache; /* cache for buffers */
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};
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/* per-bio data */
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struct dm_verity_fec_io {
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struct rs_control *rs; /* Reed-Solomon state */
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int erasures[DM_VERITY_FEC_MAX_RSN]; /* erasures for decode_rs8 */
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u8 *bufs[DM_VERITY_FEC_BUF_MAX]; /* bufs for deinterleaving */
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unsigned nbufs; /* number of buffers allocated */
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u8 *output; /* buffer for corrected output */
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size_t output_pos;
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unsigned level; /* recursion level */
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};
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#ifdef CONFIG_DM_VERITY_FEC
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/* each feature parameter requires a value */
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#define DM_VERITY_OPTS_FEC 8
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extern bool verity_fec_is_enabled(struct dm_verity *v);
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extern int verity_fec_decode(struct dm_verity *v, struct dm_verity_io *io,
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enum verity_block_type type, sector_t block,
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u8 *dest, struct bvec_iter *iter);
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extern unsigned verity_fec_status_table(struct dm_verity *v, unsigned sz,
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char *result, unsigned maxlen);
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extern void verity_fec_finish_io(struct dm_verity_io *io);
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extern void verity_fec_init_io(struct dm_verity_io *io);
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extern bool verity_is_fec_opt_arg(const char *arg_name);
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extern int verity_fec_parse_opt_args(struct dm_arg_set *as,
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struct dm_verity *v, unsigned *argc,
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const char *arg_name);
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extern void verity_fec_dtr(struct dm_verity *v);
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extern int verity_fec_ctr_alloc(struct dm_verity *v);
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extern int verity_fec_ctr(struct dm_verity *v);
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#else /* !CONFIG_DM_VERITY_FEC */
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#define DM_VERITY_OPTS_FEC 0
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static inline bool verity_fec_is_enabled(struct dm_verity *v)
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{
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return false;
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}
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static inline int verity_fec_decode(struct dm_verity *v,
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struct dm_verity_io *io,
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enum verity_block_type type,
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sector_t block, u8 *dest,
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struct bvec_iter *iter)
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{
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return -EOPNOTSUPP;
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}
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static inline unsigned verity_fec_status_table(struct dm_verity *v,
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unsigned sz, char *result,
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unsigned maxlen)
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{
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return sz;
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}
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static inline void verity_fec_finish_io(struct dm_verity_io *io)
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{
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}
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static inline void verity_fec_init_io(struct dm_verity_io *io)
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{
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}
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static inline bool verity_is_fec_opt_arg(const char *arg_name)
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{
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return false;
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}
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static inline int verity_fec_parse_opt_args(struct dm_arg_set *as,
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struct dm_verity *v,
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unsigned *argc,
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const char *arg_name)
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{
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return -EINVAL;
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}
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static inline void verity_fec_dtr(struct dm_verity *v)
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{
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}
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static inline int verity_fec_ctr_alloc(struct dm_verity *v)
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{
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return 0;
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}
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static inline int verity_fec_ctr(struct dm_verity *v)
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{
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return 0;
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}
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#endif /* CONFIG_DM_VERITY_FEC */
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#endif /* DM_VERITY_FEC_H */
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