From: Chao Yu Date: Thu, 21 May 2026 02:15:05 +0000 (+0800) Subject: f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e0288584baa5dc41df4a829a023c4c1b33fe53d7;p=thirdparty%2Flinux.git f2fs: atomic: fix UAF issue on f2fs_inode_info.atomic_inode - ioctl(F2FS_IOC_GARBAGE_COLLECT_RANGE) - shrink - f2fs_gc - gc_data_segment - ra_data_block(cow_inode) - mapping = F2FS_I(inode)->atomic_inode->i_mapping : f2fs_is_cow_file(cow_inode) is true - f2fs_evict_inode(atomic_inode) - clear_inode_flag(fi->cow_inode, FI_COW_FILE) - F2FS_I(fi->cow_inode)->atomic_inode = NULL ... - truncate_inode_pages_final(atomic_inode) - f2fs_grab_cache_folio(mapping) : create folio in atomic_inode->mapping - clear_inode(atomic_inode) - BUG_ON(atomic_inode->i_data.nrpages) We need to add a reference on fi->atomic_inode before using its mapping field during garbage collection, otherwise, it will cause UAF issue. Cc: stable@kernel.org Cc: Daeho Jeong Cc: Sunmin Jeong Fixes: 3db1de0e582c ("f2fs: change the current atomic write way") Fixes: f18d00769336 ("f2fs: use meta inode for GC of COW file") Signed-off-by: Chao Yu Signed-off-by: Jaegeuk Kim --- diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c index 99bc598898251..69e0a867219d1 100644 --- a/fs/f2fs/gc.c +++ b/fs/f2fs/gc.c @@ -1220,8 +1220,8 @@ static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum, static int ra_data_block(struct inode *inode, pgoff_t index) { struct f2fs_sb_info *sbi = F2FS_I_SB(inode); - struct address_space *mapping = f2fs_is_cow_file(inode) ? - F2FS_I(inode)->atomic_inode->i_mapping : inode->i_mapping; + struct address_space *mapping = inode->i_mapping; + struct inode *atomic_inode = NULL; struct dnode_of_data dn; struct folio *folio, *efolio; struct f2fs_io_info fio = { @@ -1236,9 +1236,22 @@ static int ra_data_block(struct inode *inode, pgoff_t index) }; int err = 0; + f2fs_down_read(&F2FS_I(inode)->i_sem); + if (f2fs_is_cow_file(inode)) { + atomic_inode = igrab(F2FS_I(inode)->atomic_inode); + if (!atomic_inode) { + f2fs_up_read(&F2FS_I(inode)->i_sem); + return -EBUSY; + } + mapping = atomic_inode->i_mapping; + } + f2fs_up_read(&F2FS_I(inode)->i_sem); + folio = f2fs_grab_cache_folio(mapping, index, true); - if (IS_ERR(folio)) - return PTR_ERR(folio); + if (IS_ERR(folio)) { + err = PTR_ERR(folio); + goto out_iput; + } if (f2fs_lookup_read_extent_cache_block(inode, index, &dn.data_blkaddr)) { @@ -1299,11 +1312,16 @@ got_it: f2fs_update_iostat(sbi, inode, FS_DATA_READ_IO, F2FS_BLKSIZE); f2fs_update_iostat(sbi, NULL, FS_GDATA_READ_IO, F2FS_BLKSIZE); + if (atomic_inode) + iput(atomic_inode); return 0; put_encrypted_page: f2fs_put_page(fio.encrypted_page, true); put_folio: f2fs_folio_put(folio, true); +out_iput: + if (atomic_inode) + iput(atomic_inode); return err; } @@ -1314,8 +1332,8 @@ put_folio: static int move_data_block(struct inode *inode, block_t bidx, int gc_type, unsigned int segno, int off) { - struct address_space *mapping = f2fs_is_cow_file(inode) ? - F2FS_I(inode)->atomic_inode->i_mapping : inode->i_mapping; + struct address_space *mapping = inode->i_mapping; + struct inode *atomic_inode = NULL; struct f2fs_io_info fio = { .sbi = F2FS_I_SB(inode), .ino = inode->i_ino, @@ -1337,10 +1355,23 @@ static int move_data_block(struct inode *inode, block_t bidx, (fio.sbi->gc_mode != GC_URGENT_HIGH) ? CURSEG_ALL_DATA_ATGC : CURSEG_COLD_DATA; + f2fs_down_read(&F2FS_I(inode)->i_sem); + if (f2fs_is_cow_file(inode)) { + atomic_inode = igrab(F2FS_I(inode)->atomic_inode); + if (!atomic_inode) { + f2fs_up_read(&F2FS_I(inode)->i_sem); + return -EBUSY; + } + mapping = atomic_inode->i_mapping; + } + f2fs_up_read(&F2FS_I(inode)->i_sem); + /* do not read out */ folio = f2fs_grab_cache_folio(mapping, bidx, false); - if (IS_ERR(folio)) - return PTR_ERR(folio); + if (IS_ERR(folio)) { + err = PTR_ERR(folio); + goto out_iput; + } if (!check_valid_map(F2FS_I_SB(inode), segno, off)) { err = -ENOENT; @@ -1473,6 +1504,9 @@ out: folio_unlock(folio); folio_end_dropbehind(folio); folio_put(folio); +out_iput: + if (atomic_inode) + iput(atomic_inode); return err; } diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c index 1694726122e60..939d75663a407 100644 --- a/fs/f2fs/inode.c +++ b/fs/f2fs/inode.c @@ -863,10 +863,15 @@ void f2fs_evict_inode(struct inode *inode) f2fs_abort_atomic_write(inode, true); if (fi->cow_inode && f2fs_is_cow_file(fi->cow_inode)) { - clear_inode_flag(fi->cow_inode, FI_COW_FILE); - F2FS_I(fi->cow_inode)->atomic_inode = NULL; - iput(fi->cow_inode); + struct inode *cow_inode = fi->cow_inode; + + f2fs_down_write(&F2FS_I(cow_inode)->i_sem); + clear_inode_flag(cow_inode, FI_COW_FILE); + F2FS_I(cow_inode)->atomic_inode = NULL; fi->cow_inode = NULL; + f2fs_up_write(&F2FS_I(cow_inode)->i_sem); + + iput(cow_inode); } trace_f2fs_evict_inode(inode);