Hi Carpenter,
I guess this may cause illegal memory access error as follows:
generic_perform_write
--a_ops->write_begin(file, mapping, pos, bytes, flags, &page, &fsdata);
--ocfs2_write_begin_nolock
--ocfs2_grab_pages_for_write
--return -EAGAIN if not enough pages
--'fsdata' will be uninitialized
--a_ops->write_end(file, mapping, pos, bytes, copied, page, fsdata);
--ocfs2_write_end_nolock
--the access of wc->w_di_bh->b_data will cause error.
if so, I suggest not eating error code and let upper level to handle
this problem.
On 2016-3-9 18:25, Dan Carpenter wrote:
> Hello Ryan Ding,
>
> The patch fbe25fb91af5: "ocfs2: fix sparse file & data ordering issue
> in direct io" from Feb 25, 2016, leads to the following static
> checker warning:
>
> fs/ocfs2/aops.c:2242 ocfs2_dio_get_block()
> error: potentially dereferencing uninitialized 'wc'.
>
> fs/ocfs2/aops.c
> 2235
> 2236 ret = ocfs2_write_begin_nolock(inode->i_mapping, pos, len,
> 2237 OCFS2_WRITE_DIRECT, NULL,
> 2238 (void **)&wc, di_bh, NULL);
> ^^^^^^^^^^^^
>
> See commit 5cffff9e2986 ('ocfs2: Fix ocfs2_page_mkwrite()') for an
> explanation why a zero return here does not imply that "wc" has been
> initialized.
>
> 2239 if (ret) {
> 2240 mlog_errno(ret);
> 2241 goto unlock;
> 2242 }
> 2243
> 2244 desc = &wc->w_desc[0];
> 2245
> 2246 p_blkno = ocfs2_clusters_to_blocks(inode->i_sb, desc->c_phys);
>
> regards,
> dan carpenter
>
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>
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