Commit 6f7ab6d4 authored by Artem Bityutskiy's avatar Artem Bityutskiy
Browse files

UBIFS: fix no_chk_data_crc 



When data CRC checking is disabled, UBIFS returns incorrect return
code from the 'try_read_node()' function (0 instead of 1, which means
CRC error), which make the caller re-read the data node again, but using
a different code patch, so the second read is fine. Thus, we read the
same node twice. And the result of this is that UBIFS is slower
with no_chk_data_crc option than it is with chk_data_crc option.
This patches fixes the problem.

Reported-by: default avatarReuben Dowle <Reuben.Dowle@navico.com>
Signed-off-by: default avatarArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
parent 6ba87c9b

fs/ubifs/io.c

+14 −8
Original line number Diff line number Diff line
@@ -75,7 +75,7 @@ void ubifs_ro_mode(struct ubifs_info *c, int err) 
 * @lnum: logical eraseblock number

 * @offs: offset within the logical eraseblock

 * @quiet: print no messages

 * @chk_crc: indicates whether to always check the CRC

 * @must_chk_crc: indicates whether to always check the CRC

 *

 * This function checks node magic number and CRC checksum. This function also

 * validates node length to prevent UBIFS from becoming crazy when an attacker
@@ -83,11 +83,17 @@ void ubifs_ro_mode(struct ubifs_info *c, int err) 
 * node length in the common header could cause UBIFS to read memory outside of

 * allocated buffer when checking the CRC checksum.

 *

 * This function returns zero in case of success %-EUCLEAN in case of bad CRC

 * or magic.

 * This function may skip data nodes CRC checking if @c->no_chk_data_crc is

 * true, which is controlled by corresponding UBIFS mount option. However, if

 * @must_chk_crc is true, then @c->no_chk_data_crc is ignored and CRC is

 * checked. Similarly, if @c->always_chk_crc is true, @c->no_chk_data_crc is

 * ignored and CRC is checked.

 *

 * This function returns zero in case of success and %-EUCLEAN in case of bad

 * CRC or magic.

 */

int ubifs_check_node(const struct ubifs_info *c, const void *buf, int lnum,

		     int offs, int quiet, int chk_crc)

		     int offs, int quiet, int must_chk_crc)

{

	int err = -EINVAL, type, node_len;

	uint32_t crc, node_crc, magic;
@@ -123,8 +129,8 @@ int ubifs_check_node(const struct ubifs_info *c, const void *buf, int lnum, 
		   node_len > c->ranges[type].max_len)

		goto out_len;



	if (!chk_crc && type == UBIFS_DATA_NODE && !c->always_chk_crc)

		if (c->no_chk_data_crc)

	if (!must_chk_crc && type == UBIFS_DATA_NODE && !c->always_chk_crc &&

	     c->no_chk_data_crc)

		return 0;



	crc = crc32(UBIFS_CRC32_INIT, buf + 8, node_len - 8);

fs/ubifs/tnc.c

+8 −4
Original line number Diff line number Diff line
@@ -443,6 +443,11 @@ static int tnc_read_node_nm(struct ubifs_info *c, struct ubifs_zbranch *zbr, 
 * This function performs that same function as ubifs_read_node except that

 * it does not require that there is actually a node present and instead

 * the return code indicates if a node was read.

 *

 * Note, this function does not check CRC of data nodes if @c->no_chk_data_crc

 * is true (it is controlled by corresponding mount option). However, if

 * @c->always_chk_crc is true, @c->no_chk_data_crc is ignored and CRC is always

 * checked.

 */

static int try_read_node(const struct ubifs_info *c, void *buf, int type,

			 int len, int lnum, int offs)
@@ -470,9 +475,8 @@ static int try_read_node(const struct ubifs_info *c, void *buf, int type, 
	if (node_len != len)

		return 0;



	if (type == UBIFS_DATA_NODE && !c->always_chk_crc)

		if (c->no_chk_data_crc)

			return 0;

	if (type == UBIFS_DATA_NODE && !c->always_chk_crc && c->no_chk_data_crc)

		return 1;



	crc = crc32(UBIFS_CRC32_INIT, buf + 8, node_len - 8);

	node_crc = le32_to_cpu(ch->crc);
@@ -1506,7 +1510,7 @@ out: 
 *

 * Note, if the bulk-read buffer length (@bu->buf_len) is known, this function

 * makes sure bulk-read nodes fit the buffer. Otherwise, this function prepares

 * maxumum possible amount of nodes for bulk-read.

 * maximum possible amount of nodes for bulk-read.

 */

int ubifs_tnc_get_bu_keys(struct ubifs_info *c, struct bu_info *bu)

{

fs/ubifs/ubifs.h

+1 −1
Original line number Diff line number Diff line
@@ -1428,7 +1428,7 @@ int ubifs_read_node_wbuf(struct ubifs_wbuf *wbuf, void *buf, int type, int len, 
int ubifs_write_node(struct ubifs_info *c, void *node, int len, int lnum,

		     int offs, int dtype);

int ubifs_check_node(const struct ubifs_info *c, const void *buf, int lnum,

		     int offs, int quiet, int chk_crc);

		     int offs, int quiet, int must_chk_crc);

void ubifs_prepare_node(struct ubifs_info *c, void *buf, int len, int pad);

void ubifs_prep_grp_node(struct ubifs_info *c, void *node, int len, int last);

int ubifs_io_init(struct ubifs_info *c);

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