6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> [ Upstream commit 3a23787ca8756920d65fda39f41353a4be1d1642 ] syzbot reported a null-ptr-deref in fuse_read_args_fill: fuse_read_folio+0xb0/0x100 fs/fuse/file.c:905 filemap_read_folio+0xc6/0x2a0 mm/filemap.c:2367 do_read_cache_folio+0x263/0x5c0 mm/filemap.c:3825 read_mapping_folio include/linux/pagemap.h:1011 [inline] erofs_bread+0x34d/0x7e0 fs/erofs/data.c:41 erofs_read_superblock fs/erofs/super.c:281 [inline] erofs_fc_fill_super+0x2b9/0x2500 fs/erofs/super.c:625 Unlike most filesystems, some network filesystems and FUSE need unavoidable valid `file` pointers for their read I/Os [1]. Anyway, those use cases need to be supported too. [1] https://docs.kernel.org/filesystems/vfs.html Reported-by: syzbot+0b1279812c46e48bb0c1@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://lore.kernel.org/r/6727bbdf.050a0220.3c8d68.0a7e.GAE@xxxxxxxxxx Fixes: fb176750266a ("erofs: add file-backed mount support") Tested-by: syzbot+0b1279812c46e48bb0c1@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20241114234905.1873723-1-hsiangkao@xxxxxxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/erofs/data.c | 10 ++++++---- fs/erofs/internal.h | 1 + 2 files changed, 7 insertions(+), 4 deletions(-) diff --git a/fs/erofs/data.c b/fs/erofs/data.c index 61debd799cf90..fa51437e1d99d 100644 --- a/fs/erofs/data.c +++ b/fs/erofs/data.c @@ -38,7 +38,7 @@ void *erofs_bread(struct erofs_buf *buf, erofs_off_t offset, } if (!folio || !folio_contains(folio, index)) { erofs_put_metabuf(buf); - folio = read_mapping_folio(buf->mapping, index, NULL); + folio = read_mapping_folio(buf->mapping, index, buf->file); if (IS_ERR(folio)) return folio; } @@ -61,9 +61,11 @@ void erofs_init_metabuf(struct erofs_buf *buf, struct super_block *sb) { struct erofs_sb_info *sbi = EROFS_SB(sb); - if (erofs_is_fileio_mode(sbi)) - buf->mapping = file_inode(sbi->fdev)->i_mapping; - else if (erofs_is_fscache_mode(sb)) + buf->file = NULL; + if (erofs_is_fileio_mode(sbi)) { + buf->file = sbi->fdev; /* some fs like FUSE needs it */ + buf->mapping = buf->file->f_mapping; + } else if (erofs_is_fscache_mode(sb)) buf->mapping = sbi->s_fscache->inode->i_mapping; else buf->mapping = sb->s_bdev->bd_mapping; diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h index 4efd578d7c627..9b03c8f323a76 100644 --- a/fs/erofs/internal.h +++ b/fs/erofs/internal.h @@ -221,6 +221,7 @@ enum erofs_kmap_type { struct erofs_buf { struct address_space *mapping; + struct file *file; struct page *page; void *base; enum erofs_kmap_type kmap_type; -- 2.43.0
