Dan Carpenter
2016-Mar-09 10:25 UTC
[Ocfs2-devel] ocfs2: fix sparse file & data ordering issue in direct io
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
Dan Carpenter
2016-Nov-15 10:33 UTC
[Ocfs2-devel] ocfs2: fix sparse file & data ordering issue in direct io
I never got a response on this. I was looking at it today and it still looks buggy to me. regards, dan carpenter On Wed, Mar 09, 2016 at 01:25:05PM +0300, 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
piaojun
2016-Nov-17 11:58 UTC
[Ocfs2-devel] ocfs2: fix sparse file & data ordering issue in direct io
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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