[bug report] f2fs: fix to avoid reading out encrypted data in page cache

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Chao Yu,

The patch 78682f794479: "f2fs: fix to avoid reading out encrypted
data in page cache" from Jul 3, 2016, leads to the following static
checker warning:

	fs/f2fs/data.c:1123 f2fs_mpage_readpages()
	error: 'bio' dereferencing possible ERR_PTR()

fs/f2fs/data.c
  1093                  }
  1094                  if (bio == NULL) {
  1095                          bio = f2fs_grab_bio(inode, block_nr, nr_pages);
  1096                          if (IS_ERR(bio))
                                    ^^^^^^^^^^
It's an error pointer.

  1097                                  goto set_error_page;
  1098                          bio_set_op_attrs(bio, REQ_OP_READ, 0);
  1099                  }
  1100  
  1101                  if (bio_add_page(bio, page, blocksize, 0) < blocksize)
  1102                          goto submit_and_realloc;
  1103  
  1104                  last_block_in_bio = block_nr;
  1105                  goto next_page;
  1106  set_error_page:
  1107                  SetPageError(page);
  1108                  zero_user_segment(page, 0, PAGE_SIZE);
  1109                  unlock_page(page);
  1110                  goto next_page;
  1111  confused:
  1112                  if (bio) {
  1113                          __submit_bio(F2FS_I_SB(inode), bio, DATA);
  1114                          bio = NULL;
  1115                  }
  1116                  unlock_page(page);
  1117  next_page:
  1118                  if (pages)
  1119                          put_page(page);
  1120          }
  1121          BUG_ON(pages && !list_empty(pages));
  1122          if (bio)
  1123                  __submit_bio(F2FS_I_SB(inode), bio, DATA);
                                                       ^^^
Dereferenced.

  1124          return 0;

regards,
dan carpenter

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