Commit 366911cd authored by David Howells's avatar David Howells
Browse files

afs: Fix directory entry size calculation 



The number of dirent records used by an AFS directory entry should be
calculated using the assumption that there is a 16-byte name field in the
first block, rather than a 20-byte name field (which is actually the case).
This miscalculation is historic and effectively standard, so we have to use
it.

The calculation we need to use is:

	1 + (((strlen(name) + 1) + 15) >> 5)

where we are adding one to the strlen() result to account for the NUL
termination.

Fix this by the following means:

 (1) Create an inline function to do the calculation for a given name
     length.

 (2) Use the function to calculate the number of records used for a dirent
     in afs_dir_iterate_block().

     Use this to move the over-end check out of the loop since it only
     needs to be done once.

     Further use this to only go through the loop for the 2nd+ records
     composing an entry.  The only test there now is for if the record is
     allocated - and we already checked the first block at the top of the
     outer loop.

 (3) Add a max name length check in afs_dir_iterate_block().

 (4) Make afs_edit_dir_add() and afs_edit_dir_remove() use the function
     from (1) to calculate the number of blocks rather than doing it
     incorrectly themselves.

Fixes: 63a4681f ("afs: Locally edit directory data for mkdir/create/unlink/...")
Fixes: ^1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Tested-by: default avatarMarc Dionne <marc.dionne@auristor.com>
parent 26982a89

fs/afs/dir.c

+26 −23
Original line number Diff line number Diff line
@@ -350,7 +350,7 @@ static int afs_dir_iterate_block(struct afs_vnode *dvnode, 
				 unsigned blkoff)

{

	union afs_xdr_dirent *dire;

	unsigned offset, next, curr;

	unsigned offset, next, curr, nr_slots;

	size_t nlen;

	int tmp;
@@ -363,13 +363,12 @@ static int afs_dir_iterate_block(struct afs_vnode *dvnode, 
	     offset < AFS_DIR_SLOTS_PER_BLOCK;

	     offset = next

	     ) {

		next = offset + 1;



		/* skip entries marked unused in the bitmap */

		if (!(block->hdr.bitmap[offset / 8] &

		      (1 << (offset % 8)))) {

			_debug("ENT[%zu.%u]: unused",

			       blkoff / sizeof(union afs_xdr_dir_block), offset);

			next = offset + 1;

			if (offset >= curr)

				ctx->pos = blkoff +

					next * sizeof(union afs_xdr_dirent);
@@ -381,35 +380,39 @@ static int afs_dir_iterate_block(struct afs_vnode *dvnode, 
		nlen = strnlen(dire->u.name,

			       sizeof(*block) -

			       offset * sizeof(union afs_xdr_dirent));

		if (nlen > AFSNAMEMAX - 1) {

			_debug("ENT[%zu]: name too long (len %u/%zu)",

			       blkoff / sizeof(union afs_xdr_dir_block),

			       offset, nlen);

			return afs_bad(dvnode, afs_file_error_dir_name_too_long);

		}



		_debug("ENT[%zu.%u]: %s %zu \"%s\"",

		       blkoff / sizeof(union afs_xdr_dir_block), offset,

		       (offset < curr ? "skip" : "fill"),

		       nlen, dire->u.name);



		/* work out where the next possible entry is */

		for (tmp = nlen; tmp > 15; tmp -= sizeof(union afs_xdr_dirent)) {

			if (next >= AFS_DIR_SLOTS_PER_BLOCK) {

		nr_slots = afs_dir_calc_slots(nlen);

		next = offset + nr_slots;

		if (next > AFS_DIR_SLOTS_PER_BLOCK) {

			_debug("ENT[%zu.%u]:"

				       " %u travelled beyond end dir block"

				       " (len %u/%zu)",

			       " %u extends beyond end dir block"

			       " (len %zu)",

			       blkoff / sizeof(union afs_xdr_dir_block),

				       offset, next, tmp, nlen);

			       offset, next, nlen);

			return afs_bad(dvnode, afs_file_error_dir_over_end);

		}

			if (!(block->hdr.bitmap[next / 8] &

			      (1 << (next % 8)))) {

				_debug("ENT[%zu.%u]:"

				       " %u unmarked extension (len %u/%zu)",



		/* Check that the name-extension dirents are all allocated */

		for (tmp = 1; tmp < nr_slots; tmp++) {

			unsigned int ix = offset + tmp;

			if (!(block->hdr.bitmap[ix / 8] & (1 << (ix % 8)))) {

				_debug("ENT[%zu.u]:"

				       " %u unmarked extension (%u/%u)",

				       blkoff / sizeof(union afs_xdr_dir_block),

				       offset, next, tmp, nlen);

				       offset, tmp, nr_slots);

				return afs_bad(dvnode, afs_file_error_dir_unmarked_ext);

			}



			_debug("ENT[%zu.%u]: ext %u/%zu",

			       blkoff / sizeof(union afs_xdr_dir_block),

			       next, tmp, nlen);

			next++;

		}



		/* skip if starts before the current position */

fs/afs/dir_edit.c

+2 −4
Original line number Diff line number Diff line
@@ -215,8 +215,7 @@ void afs_edit_dir_add(struct afs_vnode *vnode, 
	}



	/* Work out how many slots we're going to need. */

	need_slots = round_up(12 + name->len + 1 + 4, AFS_DIR_DIRENT_SIZE);

	need_slots /= AFS_DIR_DIRENT_SIZE;

	need_slots = afs_dir_calc_slots(name->len);



	meta_page = kmap(page0);

	meta = &meta_page->blocks[0];
@@ -393,8 +392,7 @@ void afs_edit_dir_remove(struct afs_vnode *vnode, 
	}



	/* Work out how many slots we're going to discard. */

	need_slots = round_up(12 + name->len + 1 + 4, AFS_DIR_DIRENT_SIZE);

	need_slots /= AFS_DIR_DIRENT_SIZE;

	need_slots = afs_dir_calc_slots(name->len);



	meta_page = kmap(page0);

	meta = &meta_page->blocks[0];

fs/afs/xdr_fs.h

+13 −1
Original line number Diff line number Diff line
@@ -58,7 +58,8 @@ union afs_xdr_dirent { 
		/* When determining the number of dirent slots needed to

		 * represent a directory entry, name should be assumed to be 16

		 * bytes, due to a now-standardised (mis)calculation, but it is

		 * in fact 20 bytes in size.

		 * in fact 20 bytes in size.  afs_dir_calc_slots() should be

		 * used for this.

		 *

		 * For names longer than (16 or) 20 bytes, extra slots should

		 * be annexed to this one using the extended_name format.
@@ -101,4 +102,15 @@ struct afs_xdr_dir_page { 
	union afs_xdr_dir_block	blocks[AFS_DIR_BLOCKS_PER_PAGE];

};



/*

 * Calculate the number of dirent slots required for any given name length.

 * The calculation is made assuming the part of the name in the first slot is

 * 16 bytes, rather than 20, but this miscalculation is now standardised.

 */

static inline unsigned int afs_dir_calc_slots(size_t name_len)

{

	name_len++; /* NUL-terminated */

	return 1 + ((name_len + 15) / AFS_DIR_DIRENT_SIZE);

}



#endif /* XDR_FS_H */

include/trace/events/afs.h

+2 −0
Original line number Diff line number Diff line
@@ -231,6 +231,7 @@ enum afs_file_error { 
	afs_file_error_dir_bad_magic,

	afs_file_error_dir_big,

	afs_file_error_dir_missing_page,

	afs_file_error_dir_name_too_long,

	afs_file_error_dir_over_end,

	afs_file_error_dir_small,

	afs_file_error_dir_unmarked_ext,
@@ -488,6 +489,7 @@ enum afs_cb_break_reason { 
	EM(afs_file_error_dir_bad_magic,	"DIR_BAD_MAGIC")	\

	EM(afs_file_error_dir_big,		"DIR_BIG")		\

	EM(afs_file_error_dir_missing_page,	"DIR_MISSING_PAGE")	\

	EM(afs_file_error_dir_name_too_long,	"DIR_NAME_TOO_LONG")	\

	EM(afs_file_error_dir_over_end,		"DIR_ENT_OVER_END")	\

	EM(afs_file_error_dir_small,		"DIR_SMALL")		\

	EM(afs_file_error_dir_unmarked_ext,	"DIR_UNMARKED_EXT")	\