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xfs: clean up memory management in xattr scrub [v24.5]

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Currently, the extended attribute scrubber uses a single VLA to store
 all the context information needed in various parts of the scrubber
 code.  This includes xattr leaf block space usage bitmaps, and the value
 buffer used to check the correctness of remote xattr value block
 headers.  We try to minimize the insanity through the use of helper
 functions, but this is a memory management nightmare.  Clean this up by
 making the bitmap and value pointers explicit members of struct
 xchk_xattr_buf.
 
 Second, strengthen the xattr checking by teaching it to look for overlapping
 data structures in the shortform attr data.
 
 Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Merge tag 'scrub-fix-xattr-memory-mgmt-6.4_2023-04-11' of git://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into guilt/xfs-for-next

xfs: clean up memory management in xattr scrub [v24.5]

Currently, the extended attribute scrubber uses a single VLA to store
all the context information needed in various parts of the scrubber
code.  This includes xattr leaf block space usage bitmaps, and the value
buffer used to check the correctness of remote xattr value block
headers.  We try to minimize the insanity through the use of helper
functions, but this is a memory management nightmare.  Clean this up by
making the bitmap and value pointers explicit members of struct
xchk_xattr_buf.

Second, strengthen the xattr checking by teaching it to look for overlapping
data structures in the shortform attr data.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
This commit is contained in:
Dave Chinner 2023-04-14 07:11:10 +10:00 committed by Dave Chinner
commit bb09d76599
4 changed files with 239 additions and 140 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

306
fs/xfs/scrub/attr.c
View File

@ -15,11 +15,51 @@
#include "xfs_da_btree.h"
#include "xfs_attr.h"
#include "xfs_attr_leaf.h"
#include "xfs_attr_sf.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
#include "scrub/dabtree.h"
#include "scrub/attr.h"
/* Free the buffers linked from the xattr buffer. */
static void
xchk_xattr_buf_cleanup(
void *priv)
{
struct xchk_xattr_buf *ab = priv;
kvfree(ab->freemap);
ab->freemap = NULL;
kvfree(ab->usedmap);
ab->usedmap = NULL;
kvfree(ab->value);
ab->value = NULL;
ab->value_sz = 0;
}
/*
* Allocate the free space bitmap if we're trying harder; there are leaf blocks
* in the attr fork; or we can't tell if there are leaf blocks.
*/
static inline bool
xchk_xattr_want_freemap(
struct xfs_scrub *sc)
{
struct xfs_ifork *ifp;
if (sc->flags & XCHK_TRY_HARDER)
return true;
if (!sc->ip)
return true;
ifp = xfs_ifork_ptr(sc->ip, XFS_ATTR_FORK);
if (!ifp)
return false;
return xfs_ifork_has_extents(ifp);
}
/*
* Allocate enough memory to hold an attr value and attr block bitmaps,
* reallocating the buffer if necessary. Buffer contents are not preserved
@ -28,41 +68,49 @@
static int
xchk_setup_xattr_buf(
struct xfs_scrub *sc,
size_t value_size,
gfp_t flags)
size_t value_size)
{
size_t sz;
size_t bmp_sz;
struct xchk_xattr_buf *ab = sc->buf;
void *new_val;
/*
* We need enough space to read an xattr value from the file or enough
* space to hold three copies of the xattr free space bitmap. We don't
* need the buffer space for both purposes at the same time.
*/
sz = 3 * sizeof(long) * BITS_TO_LONGS(sc->mp->m_attr_geo->blksize);
sz = max_t(size_t, sz, value_size);
bmp_sz = sizeof(long) * BITS_TO_LONGS(sc->mp->m_attr_geo->blksize);
/*
* If there's already a buffer, figure out if we need to reallocate it
* to accommodate a larger size.
*/
if (ab) {
if (sz <= ab->sz)
return 0;
kvfree(ab);
sc->buf = NULL;
}
if (ab)
goto resize_value;
/*
* Don't zero the buffer upon allocation to avoid runtime overhead.
* All users must be careful never to read uninitialized contents.
*/
ab = kvmalloc(sizeof(*ab) + sz, flags);
ab = kvzalloc(sizeof(struct xchk_xattr_buf), XCHK_GFP_FLAGS);
if (!ab)
return -ENOMEM;
ab->sz = sz;
sc->buf = ab;
sc->buf_cleanup = xchk_xattr_buf_cleanup;
ab->usedmap = kvmalloc(bmp_sz, XCHK_GFP_FLAGS);
if (!ab->usedmap)
return -ENOMEM;
if (xchk_xattr_want_freemap(sc)) {
ab->freemap = kvmalloc(bmp_sz, XCHK_GFP_FLAGS);
if (!ab->freemap)
return -ENOMEM;
}
resize_value:
if (ab->value_sz >= value_size)
return 0;
if (ab->value) {
kvfree(ab->value);
ab->value = NULL;
ab->value_sz = 0;
}
new_val = kvmalloc(value_size, XCHK_GFP_FLAGS);
if (!new_val)
return -ENOMEM;
ab->value = new_val;
ab->value_sz = value_size;
return 0;
}
@ -79,8 +127,7 @@ xchk_setup_xattr(
* without the inode lock held, which means we can sleep.
*/
if (sc->flags & XCHK_TRY_HARDER) {
error = xchk_setup_xattr_buf(sc, XATTR_SIZE_MAX,
XCHK_GFP_FLAGS);
error = xchk_setup_xattr_buf(sc, XATTR_SIZE_MAX);
if (error)
return error;
}
@ -111,11 +158,24 @@ xchk_xattr_listent(
int namelen,
int valuelen)
{
struct xfs_da_args args = {
.op_flags = XFS_DA_OP_NOTIME,
.attr_filter = flags & XFS_ATTR_NSP_ONDISK_MASK,
.geo = context->dp->i_mount->m_attr_geo,
.whichfork = XFS_ATTR_FORK,
.dp = context->dp,
.name = name,
.namelen = namelen,
.hashval = xfs_da_hashname(name, namelen),
.trans = context->tp,
.valuelen = valuelen,
};
struct xchk_xattr_buf *ab;
struct xchk_xattr *sx;
struct xfs_da_args args = { NULL };
int error = 0;
sx = container_of(context, struct xchk_xattr, context);
ab = sx->sc->buf;
if (xchk_should_terminate(sx->sc, &error)) {
context->seen_enough = error;
@ -128,18 +188,32 @@ xchk_xattr_listent(
return;
}
/* Only one namespace bit allowed. */
if (hweight32(flags & XFS_ATTR_NSP_ONDISK_MASK) > 1) {
xchk_fblock_set_corrupt(sx->sc, XFS_ATTR_FORK, args.blkno);
goto fail_xref;
}
/* Does this name make sense? */
if (!xfs_attr_namecheck(name, namelen)) {
xchk_fblock_set_corrupt(sx->sc, XFS_ATTR_FORK, args.blkno);
return;
goto fail_xref;
}
/*
* Local xattr values are stored in the attr leaf block, so we don't
* need to retrieve the value from a remote block to detect corruption
* problems.
*/
if (flags & XFS_ATTR_LOCAL)
goto fail_xref;
/*
* Try to allocate enough memory to extrat the attr value. If that
* doesn't work, we overload the seen_enough variable to convey
* the error message back to the main scrub function.
*/
error = xchk_setup_xattr_buf(sx->sc, valuelen, XCHK_GFP_FLAGS);
error = xchk_setup_xattr_buf(sx->sc, valuelen);
if (error == -ENOMEM)
error = -EDEADLOCK;
if (error) {
@ -147,17 +221,7 @@ xchk_xattr_listent(
return;
}
args.op_flags = XFS_DA_OP_NOTIME;
args.attr_filter = flags & XFS_ATTR_NSP_ONDISK_MASK;
args.geo = context->dp->i_mount->m_attr_geo;
args.whichfork = XFS_ATTR_FORK;
args.dp = context->dp;
args.name = name;
args.namelen = namelen;
args.hashval = xfs_da_hashname(args.name, args.namelen);
args.trans = context->tp;
args.value = xchk_xattr_valuebuf(sx->sc);
args.valuelen = valuelen;
args.value = ab->value;
error = xfs_attr_get_ilocked(&args);
/* ENODATA means the hash lookup failed and the attr is bad */
@ -213,25 +277,23 @@ xchk_xattr_set_map(
STATIC bool
xchk_xattr_check_freemap(
struct xfs_scrub *sc,
unsigned long *map,
struct xfs_attr3_icleaf_hdr *leafhdr)
{
unsigned long *freemap = xchk_xattr_freemap(sc);
unsigned long *dstmap = xchk_xattr_dstmap(sc);
struct xchk_xattr_buf *ab = sc->buf;
unsigned int mapsize = sc->mp->m_attr_geo->blksize;
int i;
/* Construct bitmap of freemap contents. */
bitmap_zero(freemap, mapsize);
bitmap_zero(ab->freemap, mapsize);
for (i = 0; i < XFS_ATTR_LEAF_MAPSIZE; i++) {
if (!xchk_xattr_set_map(sc, freemap,
if (!xchk_xattr_set_map(sc, ab->freemap,
leafhdr->freemap[i].base,
leafhdr->freemap[i].size))
return false;
}
/* Look for bits that are set in freemap and are marked in use. */
return bitmap_and(dstmap, freemap, map, mapsize) == 0;
return !bitmap_intersects(ab->freemap, ab->usedmap, mapsize);
}
/*
@ -251,7 +313,7 @@ xchk_xattr_entry(
__u32 *last_hashval)
{
struct xfs_mount *mp = ds->state->mp;
unsigned long *usedmap = xchk_xattr_usedmap(ds->sc);
struct xchk_xattr_buf *ab = ds->sc->buf;
char *name_end;
struct xfs_attr_leaf_name_local *lentry;
struct xfs_attr_leaf_name_remote *rentry;
@ -291,7 +353,7 @@ xchk_xattr_entry(
if (name_end > buf_end)
xchk_da_set_corrupt(ds, level);
if (!xchk_xattr_set_map(ds->sc, usedmap, nameidx, namesize))
if (!xchk_xattr_set_map(ds->sc, ab->usedmap, nameidx, namesize))
xchk_da_set_corrupt(ds, level);
if (!(ds->sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT))
*usedbytes += namesize;
@ -311,35 +373,26 @@ xchk_xattr_block(
struct xfs_attr_leafblock *leaf = bp->b_addr;
struct xfs_attr_leaf_entry *ent;
struct xfs_attr_leaf_entry *entries;
unsigned long *usedmap;
struct xchk_xattr_buf *ab = ds->sc->buf;
char *buf_end;
size_t off;
__u32 last_hashval = 0;
unsigned int usedbytes = 0;
unsigned int hdrsize;
int i;
int error;
if (*last_checked == blk->blkno)
return 0;
/* Allocate memory for block usage checking. */
error = xchk_setup_xattr_buf(ds->sc, 0, XCHK_GFP_FLAGS);
if (error == -ENOMEM)
return -EDEADLOCK;
if (error)
return error;
usedmap = xchk_xattr_usedmap(ds->sc);
*last_checked = blk->blkno;
bitmap_zero(usedmap, mp->m_attr_geo->blksize);
bitmap_zero(ab->usedmap, mp->m_attr_geo->blksize);
/* Check all the padding. */
if (xfs_has_crc(ds->sc->mp)) {
struct xfs_attr3_leafblock *leaf = bp->b_addr;
struct xfs_attr3_leafblock *leaf3 = bp->b_addr;
if (leaf->hdr.pad1 != 0 || leaf->hdr.pad2 != 0 ||
leaf->hdr.info.hdr.pad != 0)
if (leaf3->hdr.pad1 != 0 || leaf3->hdr.pad2 != 0 ||
leaf3->hdr.info.hdr.pad != 0)
xchk_da_set_corrupt(ds, level);
} else {
if (leaf->hdr.pad1 != 0 || leaf->hdr.info.pad != 0)
@ -356,7 +409,7 @@ xchk_xattr_block(
xchk_da_set_corrupt(ds, level);
if (leafhdr.firstused < hdrsize)
xchk_da_set_corrupt(ds, level);
if (!xchk_xattr_set_map(ds->sc, usedmap, 0, hdrsize))
if (!xchk_xattr_set_map(ds->sc, ab->usedmap, 0, hdrsize))
xchk_da_set_corrupt(ds, level);
if (ds->sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
@ -370,7 +423,7 @@ xchk_xattr_block(
for (i = 0, ent = entries; i < leafhdr.count; ent++, i++) {
/* Mark the leaf entry itself. */
off = (char *)ent - (char *)leaf;
if (!xchk_xattr_set_map(ds->sc, usedmap, off,
if (!xchk_xattr_set_map(ds->sc, ab->usedmap, off,
sizeof(xfs_attr_leaf_entry_t))) {
xchk_da_set_corrupt(ds, level);
goto out;
@ -384,7 +437,7 @@ xchk_xattr_block(
goto out;
}
if (!xchk_xattr_check_freemap(ds->sc, usedmap, &leafhdr))
if (!xchk_xattr_check_freemap(ds->sc, &leafhdr))
xchk_da_set_corrupt(ds, level);
if (leafhdr.usedbytes != usedbytes)
@ -468,38 +521,115 @@ out:
return error;
}
/* Check space usage of shortform attrs. */
STATIC int
xchk_xattr_check_sf(
struct xfs_scrub *sc)
{
struct xchk_xattr_buf *ab = sc->buf;
struct xfs_attr_shortform *sf;
struct xfs_attr_sf_entry *sfe;
struct xfs_attr_sf_entry *next;
struct xfs_ifork *ifp;
unsigned char *end;
int i;
int error = 0;
ifp = xfs_ifork_ptr(sc->ip, XFS_ATTR_FORK);
bitmap_zero(ab->usedmap, ifp->if_bytes);
sf = (struct xfs_attr_shortform *)sc->ip->i_af.if_u1.if_data;
end = (unsigned char *)ifp->if_u1.if_data + ifp->if_bytes;
xchk_xattr_set_map(sc, ab->usedmap, 0, sizeof(sf->hdr));
sfe = &sf->list[0];
if ((unsigned char *)sfe > end) {
xchk_fblock_set_corrupt(sc, XFS_ATTR_FORK, 0);
return 0;
}
for (i = 0; i < sf->hdr.count; i++) {
unsigned char *name = sfe->nameval;
unsigned char *value = &sfe->nameval[sfe->namelen];
if (xchk_should_terminate(sc, &error))
return error;
next = xfs_attr_sf_nextentry(sfe);
if ((unsigned char *)next > end) {
xchk_fblock_set_corrupt(sc, XFS_ATTR_FORK, 0);
break;
}
if (!xchk_xattr_set_map(sc, ab->usedmap,
(char *)sfe - (char *)sf,
sizeof(struct xfs_attr_sf_entry))) {
xchk_fblock_set_corrupt(sc, XFS_ATTR_FORK, 0);
break;
}
if (!xchk_xattr_set_map(sc, ab->usedmap,
(char *)name - (char *)sf,
sfe->namelen)) {
xchk_fblock_set_corrupt(sc, XFS_ATTR_FORK, 0);
break;
}
if (!xchk_xattr_set_map(sc, ab->usedmap,
(char *)value - (char *)sf,
sfe->valuelen)) {
xchk_fblock_set_corrupt(sc, XFS_ATTR_FORK, 0);
break;
}
sfe = next;
}
return 0;
}
/* Scrub the extended attribute metadata. */
int
xchk_xattr(
struct xfs_scrub *sc)
{
struct xchk_xattr sx;
struct xchk_xattr sx = {
.sc = sc,
.context = {
.dp = sc->ip,
.tp = sc->tp,
.resynch = 1,
.put_listent = xchk_xattr_listent,
.allow_incomplete = true,
},
};
xfs_dablk_t last_checked = -1U;
int error = 0;
if (!xfs_inode_hasattr(sc->ip))
return -ENOENT;
memset(&sx, 0, sizeof(sx));
/* Check attribute tree structure */
error = xchk_da_btree(sc, XFS_ATTR_FORK, xchk_xattr_rec,
&last_checked);
/* Allocate memory for xattr checking. */
error = xchk_setup_xattr_buf(sc, 0);
if (error == -ENOMEM)
return -EDEADLOCK;
if (error)
goto out;
return error;
/* Check the physical structure of the xattr. */
if (sc->ip->i_af.if_format == XFS_DINODE_FMT_LOCAL)
error = xchk_xattr_check_sf(sc);
else
error = xchk_da_btree(sc, XFS_ATTR_FORK, xchk_xattr_rec,
&last_checked);
if (error)
return error;
if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
goto out;
/* Check that every attr key can also be looked up by hash. */
sx.context.dp = sc->ip;
sx.context.resynch = 1;
sx.context.put_listent = xchk_xattr_listent;
sx.context.tp = sc->tp;
sx.context.allow_incomplete = true;
sx.sc = sc;
return 0;
/*
* Look up every xattr in this file by name.
* Look up every xattr in this file by name and hash.
*
* Use the backend implementation of xfs_attr_list to call
* xchk_xattr_listent on every attribute key in this inode.
@ -516,11 +646,11 @@ xchk_xattr(
*/
error = xfs_attr_list_ilocked(&sx.context);
if (!xchk_fblock_process_error(sc, XFS_ATTR_FORK, 0, &error))
goto out;
return error;
/* Did our listent function try to return any errors? */
if (sx.context.seen_enough < 0)
error = sx.context.seen_enough;
out:
return error;
return sx.context.seen_enough;
return 0;
}

60
fs/xfs/scrub/attr.h
View File

@ -10,59 +10,15 @@
* Temporary storage for online scrub and repair of extended attributes.
*/
struct xchk_xattr_buf {
/* Size of @buf, in bytes. */
size_t sz;
/* Bitmap of used space in xattr leaf blocks and shortform forks. */
unsigned long *usedmap;
/*
* Memory buffer -- either used for extracting attr values while
* walking the attributes; or for computing attr block bitmaps when
* checking the attribute tree.
*
* Each bitmap contains enough bits to track every byte in an attr
* block (rounded up to the size of an unsigned long). The attr block
* used space bitmap starts at the beginning of the buffer; the free
* space bitmap follows immediately after; and we have a third buffer
* for storing intermediate bitmap results.
*/
uint8_t buf[];
/* Bitmap of free space in xattr leaf blocks. */
unsigned long *freemap;
/* Memory buffer used to extract xattr values. */
void *value;
size_t value_sz;
};
/* A place to store attribute values. */
static inline uint8_t *
xchk_xattr_valuebuf(
struct xfs_scrub *sc)
{
struct xchk_xattr_buf *ab = sc->buf;
return ab->buf;
}
/* A bitmap of space usage computed by walking an attr leaf block. */
static inline unsigned long *
xchk_xattr_usedmap(
struct xfs_scrub *sc)
{
struct xchk_xattr_buf *ab = sc->buf;
return (unsigned long *)ab->buf;
}
/* A bitmap of free space computed by walking attr leaf block free info. */
static inline unsigned long *
xchk_xattr_freemap(
struct xfs_scrub *sc)
{
return xchk_xattr_usedmap(sc) +
BITS_TO_LONGS(sc->mp->m_attr_geo->blksize);
}
/* A bitmap used to hold temporary results. */
static inline unsigned long *
xchk_xattr_dstmap(
struct xfs_scrub *sc)
{
return xchk_xattr_freemap(sc) +
BITS_TO_LONGS(sc->mp->m_attr_geo->blksize);
}
#endif /* __XFS_SCRUB_ATTR_H__ */

3
fs/xfs/scrub/scrub.c
View File

@ -189,7 +189,10 @@ xchk_teardown(
if (sc->flags & XCHK_REAPING_DISABLED)
xchk_start_reaping(sc);
if (sc->buf) {
if (sc->buf_cleanup)
sc->buf_cleanup(sc->buf);
kvfree(sc->buf);
sc->buf_cleanup = NULL;
sc->buf = NULL;
}

10
fs/xfs/scrub/scrub.h
View File

@ -77,7 +77,17 @@ struct xfs_scrub {
*/
struct xfs_inode *ip;
/* Kernel memory buffer used by scrubbers; freed at teardown. */
void *buf;
/*
* Clean up resources owned by whatever is in the buffer. Cleanup can
* be deferred with this hook as a means for scrub functions to pass
* data to repair functions. This function must not free the buffer
* itself.
*/
void (*buf_cleanup)(void *buf);
uint ilock_flags;
/* See the XCHK/XREP state flags below. */