sorry, my analysis is wrong. -EAGAIN will be eaten only when 'type' is
OCFS2_WRITE_MMAP in ocfs2_write_begin_nolock(). so uninitialized 'wc'
will not be dereferenced in ocfs2_dio_get_block() as abnormal branch
can catch error 'ret'.
thanks,
Jun
On 2016-11-17 19:58, piaojun wrote:
> 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
>>
>> _______________________________________________
>> Ocfs2-devel mailing list
>> Ocfs2-devel@oss.oracle.com
>> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
>>
>>
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