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.
-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
