commit 9ed50b8231e37b1ae863f5dec8153b98d9f389b4 upstream. Fast symlink can be used if the on-disk symlink data is stored in the same block as the on-disk inode, so we don’t need to trigger another I/O for symlink data. However, currently fs correction could be reported _incorrectly_ if inode xattrs are too large. In fact, these should be valid images although they cannot be handled as fast symlinks. Many thanks to Colin for reporting this! Reported-by: Colin Walters <walters@xxxxxxxxxx> Reported-by: https://honggfuzz.dev/ Link: https://lore.kernel.org/r/bb2dd430-7de0-47da-ae5b-82ab2dd4d945@xxxxxxxxxxxxxxxx Fixes: 431339ba9042 ("staging: erofs: add inode operations") [ Note that it's a runtime misbehavior instead of a security issue. ] Link: https://lore.kernel.org/r/20240909031911.1174718-1-hsiangkao@xxxxxxxxxxxxxxxxx [ Gao Xiang: fix 5.4.y build warning due to `check_add_overflow`. ] Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> --- fs/erofs/inode.c | 20 ++++++-------------- 1 file changed, 6 insertions(+), 14 deletions(-) diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c index ba981076d6f2..af90d3d70a08 100644 --- a/fs/erofs/inode.c +++ b/fs/erofs/inode.c @@ -198,11 +198,14 @@ static int erofs_fill_symlink(struct inode *inode, void *data, unsigned int m_pofs) { struct erofs_inode *vi = EROFS_I(inode); + loff_t off; char *lnk; - /* if it cannot be handled with fast symlink scheme */ - if (vi->datalayout != EROFS_INODE_FLAT_INLINE || - inode->i_size >= PAGE_SIZE || inode->i_size < 0) { + m_pofs += vi->xattr_isize; + /* check if it cannot be handled with fast symlink scheme */ + if (vi->datalayout != EROFS_INODE_FLAT_INLINE || inode->i_size < 0 || + check_add_overflow((loff_t)m_pofs, inode->i_size, &off) || + off > i_blocksize(inode)) { inode->i_op = &erofs_symlink_iops; return 0; } @@ -211,17 +214,6 @@ static int erofs_fill_symlink(struct inode *inode, void *data, if (!lnk) return -ENOMEM; - m_pofs += vi->xattr_isize; - /* inline symlink data shouldn't cross page boundary as well */ - if (m_pofs + inode->i_size > PAGE_SIZE) { - kfree(lnk); - erofs_err(inode->i_sb, - "inline data cross block boundary @ nid %llu", - vi->nid); - DBG_BUGON(1); - return -EFSCORRUPTED; - } - memcpy(lnk, data + m_pofs, inode->i_size); lnk[inode->i_size] = '\0'; -- 2.43.5
