As Al pointed out, " ... and while we are at it, what happens to unsigned int nameoff = le16_to_cpu(de[mid].nameoff); unsigned int matched = min(startprfx, endprfx);

struct qstr dname = QSTR_INIT(data + nameoff, unlikely(mid >= ndirents - 1) ? maxsize - nameoff : le16_to_cpu(de[mid + 1].nameoff) - nameoff);

/* string comparison without already matched prefix */ int ret = dirnamecmp(name, &dname, &matched); if le16_to_cpu(de[...].nameoff) is not monotonically increasing? I.e. what's to prevent e.g. (unsigned)-1 ending up in dname.len?

Corrupted fs image shouldn't oops the kernel.. "

Revisit the related lookup flow to address the issue.

Fixes: d72d1ce60174 ("staging: erofs: add namei functions") Cc: stable@vger.kernel.org # 4.19+ Suggested-by: Al Viro viro@ZenIV.linux.org.uk Signed-off-by: Gao Xiang gaoxiang25@huawei.com --- TODO: - fix similar issue in readdir of dir.c with another patch.

drivers/staging/erofs/namei.c | 167 ++++++++++++++++++++++-------------------- 1 file changed, 89 insertions(+), 78 deletions(-)

diff --git a/drivers/staging/erofs/namei.c b/drivers/staging/erofs/namei.c index 5596c52e246d..a1300c420e63 100644 --- a/drivers/staging/erofs/namei.c +++ b/drivers/staging/erofs/namei.c @@ -15,74 +15,76 @@

#include <trace/events/erofs.h>

-/* based on the value of qn->len is accurate */ -static inline int dirnamecmp(struct qstr *qn, - struct qstr *qd, unsigned int *matched) +struct erofs_qstr { + const unsigned char *name; + const unsigned char *end; +}; + +/* based on the end of qn is accurate and it must have the trailing '\0' */ +static inline int dirnamecmp(const struct erofs_qstr *qn, + const struct erofs_qstr *qd, + unsigned int *matched) { - unsigned int i = *matched, len = min(qn->len, qd->len); -loop: - if (unlikely(i >= len)) { - *matched = i; - if (qn->len < qd->len) { - /* - * actually (qn->len == qd->len) - * when qd->name[i] == '\0' - */ - return qd->name[i] == '\0' ? 0 : -1; + unsigned int i = *matched; + + /* + * on-disk error, let's only BUG_ON in the debugging mode. + * otherwise, it will return 1 to just skip the invalid name + * and go on (in consideration of the lookup performance). + */ + DBG_BUGON(qd->name > qd->end); + + /* qd could not have trailing '\0' */ + /* However it is absolutely safe if < qd->end */ + while (qd->name + i < qd->end && qd->name[i] != '\0') { + if (qn->name[i] != qd->name[i]) { + *matched = i; + return qn->name[i] > qd->name[i] ? 1 : -1; } - return (qn->len > qd->len); + ++i; } - - if (qn->name[i] != qd->name[i]) { - *matched = i; - return qn->name[i] > qd->name[i] ? 1 : -1; - } - - ++i; - goto loop; + *matched = i; + /* See comments in __d_alloc on the terminating NUL character */ + return qn->name[i] == '\0' ? 0 : 1; }

-static struct erofs_dirent *find_target_dirent( - struct qstr *name, - u8 *data, int maxsize) +#define nameoff_from_disk(off, sz) (le16_to_cpu(off) & ((sz) - 1)) + +static struct erofs_dirent *find_target_dirent(struct erofs_qstr *name, + u8 *data, + unsigned int dirblksize, + const int ndirents) { - unsigned int ndirents, head, back; + int head, back; unsigned int startprfx, endprfx; struct erofs_dirent *const de = (struct erofs_dirent *)data;

- /* make sure that maxsize is valid */ - BUG_ON(maxsize < sizeof(struct erofs_dirent)); - - ndirents = le16_to_cpu(de->nameoff) / sizeof(*de); - - /* corrupted dir (may be unnecessary...) */ - BUG_ON(!ndirents); - head = 0; back = ndirents - 1; startprfx = endprfx = 0;

while (head <= back) { - unsigned int mid = head + (back - head) / 2; - unsigned int nameoff = le16_to_cpu(de[mid].nameoff); + const int mid = head + (back - head) / 2; + const int nameoff = nameoff_from_disk(de[mid].nameoff, + dirblksize); unsigned int matched = min(startprfx, endprfx); - - struct qstr dname = QSTR_INIT(data + nameoff, - unlikely(mid >= ndirents - 1) ? - maxsize - nameoff : - le16_to_cpu(de[mid + 1].nameoff) - nameoff); + struct erofs_qstr dname = { + .name = data + nameoff, + .end = unlikely(mid >= ndirents - 1) ? + data + dirblksize : + data + nameoff_from_disk(de[mid + 1].nameoff, + dirblksize) + };

/* string comparison without already matched prefix */ int ret = dirnamecmp(name, &dname, &matched);

- if (unlikely(!ret)) + if (unlikely(!ret)) { return de + mid; - else if (ret > 0) { + } else if (ret > 0) { head = mid + 1; startprfx = matched; - } else if (unlikely(mid < 1)) /* fix "mid" overflow */ - break; - else { + } else { back = mid - 1; endprfx = matched; } @@ -91,12 +93,13 @@ static struct erofs_dirent *find_target_dirent( return ERR_PTR(-ENOENT); }

-static struct page *find_target_block_classic( - struct inode *dir, - struct qstr *name, int *_diff) +static struct page *find_target_block_classic(struct inode *dir, + struct erofs_qstr *name, + int *_diff, + int *_ndirents) { unsigned int startprfx, endprfx; - unsigned int head, back; + int head, back; struct address_space *const mapping = dir->i_mapping; struct page *candidate = ERR_PTR(-ENOENT);

@@ -105,33 +108,34 @@ static struct page *find_target_block_classic( back = inode_datablocks(dir) - 1;

while (head <= back) { - unsigned int mid = head + (back - head) / 2; + const int mid = head + (back - head) / 2; struct page *page = read_mapping_page(mapping, mid, NULL);

- if (IS_ERR(page)) { -exact_out: - if (!IS_ERR(candidate)) /* valid candidate */ - put_page(candidate); - return page; - } else { - int diff; - unsigned int ndirents, matched; - struct qstr dname; + if (!IS_ERR(page)) { struct erofs_dirent *de = kmap_atomic(page); - unsigned int nameoff = le16_to_cpu(de->nameoff); - - ndirents = nameoff / sizeof(*de); + const int nameoff = nameoff_from_disk(de->nameoff, + EROFS_BLKSIZ); + const int ndirents = nameoff / sizeof(*de); + int diff; + unsigned int matched; + struct erofs_qstr dname;

- /* corrupted dir (should have one entry at least) */ - BUG_ON(!ndirents || nameoff > PAGE_SIZE); + if (unlikely(!ndirents)) { + DBG_BUGON(1); + put_page(page); + page = ERR_PTR(-EIO); + goto out; + }

matched = min(startprfx, endprfx);

dname.name = (u8 *)de + nameoff; - dname.len = ndirents == 1 ? - /* since the rest of the last page is 0 */ - EROFS_BLKSIZ - nameoff - : le16_to_cpu(de[1].nameoff) - nameoff; + if (ndirents == 1) + dname.end = (u8 *)de + EROFS_BLKSIZ; + else + dname.end = (u8 *)de + + nameoff_from_disk(de[1].nameoff, + EROFS_BLKSIZ);

/* string comparison without already matched prefix */ diff = dirnamecmp(name, &dname, &matched); @@ -139,7 +143,7 @@ static struct page *find_target_block_classic(

if (unlikely(!diff)) { *_diff = 0; - goto exact_out; + goto out; } else if (diff > 0) { head = mid + 1; startprfx = matched; @@ -147,35 +151,42 @@ static struct page *find_target_block_classic( if (likely(!IS_ERR(candidate))) put_page(candidate); candidate = page; + *_ndirents = ndirents; } else { put_page(page);

- if (unlikely(mid < 1)) /* fix "mid" overflow */ - break; - back = mid - 1; endprfx = matched; } + continue; } +out: /* free if the candidate is valid */ + if (!IS_ERR(candidate)) + put_page(candidate); + return page; } *_diff = 1; return candidate; }

int erofs_namei(struct inode *dir, - struct qstr *name, - erofs_nid_t *nid, unsigned int *d_type) + struct qstr *name, + erofs_nid_t *nid, unsigned int *d_type) { - int diff; + int diff, ndirents; struct page *page; u8 *data; struct erofs_dirent *de; + struct erofs_qstr qn;

if (unlikely(!dir->i_size)) return -ENOENT;

+ qn.name = name->name; + qn.end = name->name + name->len; + diff = 1; - page = find_target_block_classic(dir, name, &diff); + page = find_target_block_classic(dir, &qn, &diff, &ndirents);

if (unlikely(IS_ERR(page))) return PTR_ERR(page); @@ -184,7 +195,7 @@ int erofs_namei(struct inode *dir, /* the target page has been mapped */ de = likely(diff) ? /* since the rest of the last page is 0 */ - find_target_dirent(name, data, EROFS_BLKSIZ) : + find_target_dirent(&qn, data, EROFS_BLKSIZ, ndirents) : (struct erofs_dirent *)data;

if (likely(!IS_ERR(de))) {