Re: [cifs:for-next 7/9] fs/cifs/file.c:3203 cifs_send_async_read() warn: unsigned 'cur_len' is never less than zero.

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added a trivial followon patch to fix this warning and pushed to
cifs-2.6.git for-next

thx
On Thu, Nov 1, 2018 at 11:35 AM kbuild test robot <lkp@xxxxxxxxx> wrote:
>
> tree:   git://git.samba.org/sfrench/cifs-2.6.git for-next
> head:   81b4dd0ea7cd93a6ebb5d6d0f22e77a463397bc2
> commit: 27d00133fadd8753e1856889dea2da4cb22910a3 [7/9] CIFS: Add support for direct I/O read
>
> New smatch warnings:
> fs/cifs/file.c:3203 cifs_send_async_read() warn: unsigned 'cur_len' is never less than zero.
>
> Old smatch warnings:
> fs/cifs/file.c:3608 cifs_read() warn: variable dereferenced before check 'tcon->ses' (see line 3583)
>
> vim +/cur_len +3203 fs/cifs/file.c
>
>   3164
>   3165  static int
>   3166  cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
>   3167                       struct cifs_sb_info *cifs_sb, struct list_head *rdata_list,
>   3168                       struct cifs_aio_ctx *ctx)
>   3169  {
>   3170          struct cifs_readdata *rdata;
>   3171          unsigned int npages, rsize, credits;
>   3172          size_t cur_len;
>   3173          int rc;
>   3174          pid_t pid;
>   3175          struct TCP_Server_Info *server;
>   3176          struct page **pagevec;
>   3177          size_t start;
>   3178          struct iov_iter direct_iov = ctx->iter;
>   3179
>   3180          server = tlink_tcon(open_file->tlink)->ses->server;
>   3181
>   3182          if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_RWPIDFORWARD)
>   3183                  pid = open_file->pid;
>   3184          else
>   3185                  pid = current->tgid;
>   3186
>   3187          if (ctx->direct_io)
>   3188                  iov_iter_advance(&direct_iov, offset - ctx->pos);
>   3189
>   3190          do {
>   3191                  rc = server->ops->wait_mtu_credits(server, cifs_sb->rsize,
>   3192                                                     &rsize, &credits);
>   3193                  if (rc)
>   3194                          break;
>   3195
>   3196                  cur_len = min_t(const size_t, len, rsize);
>   3197
>   3198                  if (ctx->direct_io) {
>   3199
>   3200                          cur_len = iov_iter_get_pages_alloc(
>   3201                                          &direct_iov, &pagevec,
>   3202                                          cur_len, &start);
> > 3203                          if (cur_len < 0) {
>   3204                                  cifs_dbg(VFS,
>   3205                                          "couldn't get user pages (cur_len=%zd)"
>   3206                                          " iter type %d"
>   3207                                          " iov_offset %zd count %zd\n",
>   3208                                          cur_len, direct_iov.type, direct_iov.iov_offset,
>   3209                                          direct_iov.count);
>   3210                                  dump_stack();
>   3211                                  break;
>   3212                          }
>   3213                          iov_iter_advance(&direct_iov, cur_len);
>   3214
>   3215                          rdata = cifs_readdata_direct_alloc(
>   3216                                          pagevec, cifs_uncached_readv_complete);
>   3217                          if (!rdata) {
>   3218                                  add_credits_and_wake_if(server, credits, 0);
>   3219                                  rc = -ENOMEM;
>   3220                                  break;
>   3221                          }
>   3222
>   3223                          npages = (cur_len + start + PAGE_SIZE-1) / PAGE_SIZE;
>   3224                          rdata->page_offset = start;
>   3225                          rdata->tailsz = npages > 1 ?
>   3226                                  cur_len-(PAGE_SIZE-start)-(npages-2)*PAGE_SIZE :
>   3227                                  cur_len;
>   3228
>   3229                  } else {
>   3230
>   3231                          npages = DIV_ROUND_UP(cur_len, PAGE_SIZE);
>   3232                          /* allocate a readdata struct */
>   3233                          rdata = cifs_readdata_alloc(npages,
>   3234                                              cifs_uncached_readv_complete);
>   3235                          if (!rdata) {
>   3236                                  add_credits_and_wake_if(server, credits, 0);
>   3237                                  rc = -ENOMEM;
>   3238                                  break;
>   3239                          }
>   3240
>   3241                          rc = cifs_read_allocate_pages(rdata, npages);
>   3242                          if (rc)
>   3243                                  goto error;
>   3244
>   3245                          rdata->tailsz = PAGE_SIZE;
>   3246                  }
>   3247
>   3248                  rdata->cfile = cifsFileInfo_get(open_file);
>   3249                  rdata->nr_pages = npages;
>   3250                  rdata->offset = offset;
>   3251                  rdata->bytes = cur_len;
>   3252                  rdata->pid = pid;
>   3253                  rdata->pagesz = PAGE_SIZE;
>   3254                  rdata->read_into_pages = cifs_uncached_read_into_pages;
>   3255                  rdata->copy_into_pages = cifs_uncached_copy_into_pages;
>   3256                  rdata->credits = credits;
>   3257                  rdata->ctx = ctx;
>   3258                  kref_get(&ctx->refcount);
>   3259
>   3260                  if (!rdata->cfile->invalidHandle ||
>   3261                      !(rc = cifs_reopen_file(rdata->cfile, true)))
>   3262                          rc = server->ops->async_readv(rdata);
>   3263  error:
>   3264                  if (rc) {
>   3265                          add_credits_and_wake_if(server, rdata->credits, 0);
>   3266                          kref_put(&rdata->refcount,
>   3267                                  cifs_uncached_readdata_release);
>   3268                          if (rc == -EAGAIN) {
>   3269                                  iov_iter_revert(&direct_iov, cur_len);
>   3270                                  continue;
>   3271                          }
>   3272                          break;
>   3273                  }
>   3274
>   3275                  list_add_tail(&rdata->list, rdata_list);
>   3276                  offset += cur_len;
>   3277                  len -= cur_len;
>   3278          } while (len > 0);
>   3279
>   3280          return rc;
>   3281  }
>   3282
>
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation



-- 
Thanks,

Steve



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