* [dhowells-fs:cifs-for-sfrench 7/9] fs/cifs/file.c:2496 cifs_write_back_from_locked_folio() error: potential null dereference 'wdata'. (cifs_writedata_alloc returns null)
@ 2022-05-27 21:26 kernel test robot
0 siblings, 0 replies; only message in thread
From: kernel test robot @ 2022-05-27 21:26 UTC (permalink / raw)
To: David Howells; +Cc: kbuild-all, linux-kernel
tree: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git cifs-for-sfrench
head: c1da8a43f0f920f86394ca254c99a91622bb3fe4
commit: 058279f48aab49f18536d30e1bb778c8b35620b1 [7/9] cifs: Trace writedata page wrangling
config: i386-randconfig-m021 (https://download.01.org/0day-ci/archive/20220528/202205280552.tAo4vYPe-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-1) 11.3.0
If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@intel.com>
smatch warnings:
fs/cifs/file.c:2496 cifs_write_back_from_locked_folio() error: potential null dereference 'wdata'. (cifs_writedata_alloc returns null)
fs/cifs/file.c:2496 cifs_write_back_from_locked_folio() error: we previously assumed 'wdata' could be null (see line 2414)
fs/cifs/file.c:2496 cifs_write_back_from_locked_folio() error: potentially dereferencing uninitialized 'wdata'.
vim +/wdata +2496 fs/cifs/file.c
2370
2371 /*
2372 * Write back the locked page and any subsequent non-locked dirty pages.
2373 */
2374 static ssize_t cifs_write_back_from_locked_folio(struct address_space *mapping,
2375 struct writeback_control *wbc,
2376 struct folio *folio,
2377 loff_t start, loff_t end)
2378 {
2379 struct inode *inode = mapping->host;
2380 struct TCP_Server_Info *server;
2381 struct cifs_writedata *wdata;
2382 struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
2383 struct cifs_credits credits_on_stack;
2384 struct cifs_credits *credits = &credits_on_stack;
2385 struct cifsFileInfo *cfile = NULL;
2386 unsigned int xid, wsize, len;
2387 loff_t i_size = i_size_read(inode);
2388 size_t max_len;
2389 long count = wbc->nr_to_write;
2390 int rc;
2391
2392 /* The folio should be locked, dirty and not undergoing writeback. */
2393 if (folio_start_writeback(folio))
2394 WARN_ON(1);
2395
2396 count -= folio_nr_pages(folio);
2397 len = folio_size(folio);
2398
2399 xid = get_xid();
2400 server = cifs_pick_channel(cifs_sb_master_tcon(cifs_sb)->ses);
2401
2402 rc = cifs_get_writable_file(CIFS_I(inode), FIND_WR_ANY, &cfile);
2403 if (rc) {
2404 cifs_dbg(VFS, "No writable handle in writepages rc=%d\n", rc);
2405 goto err_xid;
2406 }
2407
2408 rc = server->ops->wait_mtu_credits(server, cifs_sb->ctx->wsize,
2409 &wsize, credits);
2410 if (rc != 0)
2411 goto err_close;
2412
2413 wdata = cifs_writedata_alloc(cifs_writev_complete);
> 2414 if (!wdata) {
2415 rc = -ENOMEM;
2416 goto err_uncredit;
2417 }
2418
2419 wdata->sync_mode = wbc->sync_mode;
2420 wdata->offset = folio_pos(folio);
2421 wdata->pid = cfile->pid;
2422 wdata->credits = credits_on_stack;
2423 wdata->cfile = cfile;
2424 wdata->server = server;
2425 cfile = NULL;
2426
2427 /* Find all consecutive lockable dirty pages, stopping when we find a
2428 * page that is not immediately lockable, is not dirty or is missing,
2429 * or we reach the end of the range.
2430 */
2431 if (start < i_size) {
2432 /* Trim the write to the EOF; the extra data is ignored. Also
2433 * put an upper limit on the size of a single storedata op.
2434 */
2435 max_len = wsize;
2436 max_len = min_t(unsigned long long, max_len, end - start + 1);
2437 max_len = min_t(unsigned long long, max_len, i_size - start);
2438
2439 if (len < max_len) {
2440 int max_pages = INT_MAX;
2441
2442 #ifdef CONFIG_CIFS_SMB_DIRECT
2443 if (server->smbd_conn)
2444 max_pages = server->smbd_conn->max_frmr_depth;
2445 #endif
2446 max_pages -= folio_nr_pages(folio);
2447
2448 if (max_pages > 0)
2449 cifs_extend_writeback(mapping, &count, start,
2450 max_pages, max_len, &len);
2451 }
2452 len = min_t(loff_t, len, max_len);
2453 }
2454
2455 wdata->bytes = len;
2456
2457 /* We now have a contiguous set of dirty pages, each with writeback
2458 * set; the first page is still locked at this point, but all the rest
2459 * have been unlocked.
2460 */
2461 folio_unlock(folio);
2462
2463 if (start < i_size) {
2464 iov_iter_xarray(&wdata->iter, WRITE, &mapping->i_pages, start, len);
2465
2466 rc = adjust_credits(wdata->server, &wdata->credits, wdata->bytes);
2467 if (rc)
2468 goto err_wdata;
2469
2470 trace_smb3_pages_write_back(inode, start, len, 0, wdata->debug_id);
2471 if (wdata->cfile->invalidHandle)
2472 rc = -EAGAIN;
2473 else
2474 rc = wdata->server->ops->async_writev(wdata,
2475 cifs_writedata_release);
2476 if (rc >= 0) {
2477 kref_put(&wdata->refcount, cifs_writedata_release);
2478 goto err_close;
2479 }
2480 } else {
2481 /* The dirty region was entirely beyond the EOF. */
2482 trace_smb3_pages_write_beyond(inode, start, len, rc, wdata->debug_id);
2483 cifs_pages_written_back(inode, start, len, wdata->debug_id);
2484 rc = 0;
2485 }
2486
2487 err_wdata:
2488 kref_put(&wdata->refcount, cifs_writedata_release);
2489 err_uncredit:
2490 add_credits_and_wake_if(server, credits, 0);
2491 err_close:
2492 if (cfile)
2493 cifsFileInfo_put(cfile);
2494 err_xid:
2495 free_xid(xid);
> 2496 trace_smb3_pages_write_end(inode, start, len, rc, wdata->debug_id);
2497 if (rc == 0) {
2498 wbc->nr_to_write = count;
2499 } else if (is_retryable_error(rc)) {
2500 cifs_pages_write_redirty(inode, start, len, wdata->debug_id);
2501 } else {
2502 cifs_pages_write_failed(inode, start, len, wdata->debug_id);
2503 mapping_set_error(mapping, rc);
2504 }
2505 /* Indication to update ctime and mtime as close is deferred */
2506 set_bit(CIFS_INO_MODIFIED_ATTR, &CIFS_I(inode)->flags);
2507 return rc;
2508 }
2509
--
0-DAY CI Kernel Test Service
https://01.org/lkp
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2022-05-27 21:26 [dhowells-fs:cifs-for-sfrench 7/9] fs/cifs/file.c:2496 cifs_write_back_from_locked_folio() error: potential null dereference 'wdata'. (cifs_writedata_alloc returns null) kernel test robot
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