On Tue, Jan 24, 2017 at 09:04:57AM -0600, Bill O'Donnell wrote:
> On Fri, Jan 20, 2017 at 11:04:42PM +0000, Colin Ian King wrote:
> > On 20/01/17 20:47, Darrick J. Wong wrote:
> > > On Fri, Jan 20, 2017 at 01:26:12PM -0600, Eric Sandeen wrote:
> > >> On 1/20/17 8:26 AM, Colin King wrote:
> > >>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > >>>
> > >>> If pag cannot be allocated, the current error exit path will trip
> > >>> a null pointer deference error when calling xfs_buf_hash_destroy
> > >>> with a null pag. Fix this by adding a new error exit lable and
> > >>> jumping to this, avoiding the hash destroy and unnecessary kmem_free
> > >>> on pag.
> > >>>
> > >>> Fixes CoverityScan CID#1397628 ("Dereference after null check")
> > >>>
> > >>> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > >>
> > >> Hm, I think this leaves the code with issues.
> > >>
> > >>> ---
> > >>> fs/xfs/xfs_mount.c | 3 ++-
> > >>> 1 file changed, 2 insertions(+), 1 deletion(-)
> > >>>
> > >>> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> > >>> index 9b9540d..4e66cd19 100644
> > >>> --- a/fs/xfs/xfs_mount.c
> > >>> +++ b/fs/xfs/xfs_mount.c
> > >>> @@ -207,7 +207,7 @@ xfs_initialize_perag(
> > >>>
> > >>> pag = kmem_zalloc(sizeof(*pag), KM_MAYFAIL);
> > >>> if (!pag)
> > >>> - goto out_unwind;
> > >>> + goto out_unwind_pags;
> > >>
> > >> So let's say we got to index == 3 at the top of the loop, and
> > >> this fails.
> > >>
> > >> We succeeded in initializing 0, 1, and 2, but 3 failed.
> > >>
> > >> So we go to out_unwind_pags with index == 3...
> > >>
> > >>> pag->pag_agno = index;
> > >>> pag->pag_mount = mp;
> > >>> spin_lock_init(&pag->pag_ici_lock);
> > >>> @@ -242,6 +242,7 @@ xfs_initialize_perag(
> > >>> out_unwind:
> > >>> xfs_buf_hash_destroy(pag);
> > >>> kmem_free(pag);
> > >>> +out_unwind_pags:
> > >>
> > >> ... where index == 3, and:
> > >>
> > >>> for (; index > first_initialised; index--) {
> > >>> pag = radix_tree_delete(&mp->m_perag_tree, index);
> > >>
> > >> this should fail, because it never got inserted, and...
> > >>
> > >>> xfs_buf_hash_destroy(pag);
> > >>
> > >> this still tries to destroy a NULL pag, no?
> > >>
> > >> There also seems to be an existing issue w/the code where ag 0 is
> > >> never torn down in the error case, because first_initialized doesn't
> > >> stay set to 0:
> > >>
> > >> if (!first_initialised)
> > >> first_initialised = index;
> > >>
> > >> And we don't even tear down ag 1, because:
> > >>
> > >>> for (; index > first_initialised; index--) {
> > >>> pag = radix_tree_delete(&mp->m_perag_tree, index);
> > >>
> > >> when the loop reaches the first initialized AG, it stops.
> > >>
> > >> So we seem to always leak at least 2 if we managed to get far enough
> > >> to initialize them.
> > >
> > > Ugh, yeah, the the whole error exit from that function is fubar...
> > > Anyone want to clean this up?
> >
> > I may step back on this if somebody else wants to fix this up properly.
>
> I'll take it.
Acknowledged. :)
--D
> -Bill
>
>
> >
> > >
> > > --D
> > >
> > >>
> > >> -Eric
> > >>
> > >>>
> > >> --
> > >> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> > >> the body of a message to majordomo@xxxxxxxxxxxxxxx
> > >> More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
> > the body of a message to majordomo@xxxxxxxxxxxxxxx
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
