[PATCH v2 4/5] vfio: ccw: set ccw->cda to NULL defensively

Dong Jia Shi
2018-04-23T11:01:12Z

Let's avoid free on ccw->cda that points to a guest address
or an already freed memory area by setting it to NULL if memory
allocation didn't happen or failed.

Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
---
drivers/s390/cio/vfio_ccw_cp.c | 31 ++++++++++++++++++++-----------
1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index 340804b45f6a..1eef102c685e 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -491,7 +491,7 @@ static int ccwchain_fetch_direct(struct ccwchain *chain,
struct ccw1 *ccw;
struct pfn_array_table *pat;
unsigned long *idaws;
- int idaw_nr;
+ int ret;

ccw = chain->ch_ccw + idx;

@@ -511,18 +511,19 @@ static int ccwchain_fetch_direct(struct ccwchain *chain,
* needed when translating a direct ccw to a idal ccw.
*/
pat = chain->ch_pat + idx;
- if (pfn_array_table_init(pat, 1))
- return -ENOMEM;
- idaw_nr = pfn_array_alloc_pin(pat->pat_pa, cp->mdev,
- ccw->cda, ccw->count);
- if (idaw_nr < 0)
- return idaw_nr;
+ ret = pfn_array_table_init(pat, 1);
+ if (ret)
+ goto out_init;
+
+ ret = pfn_array_alloc_pin(pat->pat_pa, cp->mdev, ccw->cda, ccw->count);
+ if (ret < 0)
+ goto out_init;

/* Translate this direct ccw to a idal ccw. */
- idaws = kcalloc(idaw_nr, sizeof(*idaws), GFP_DMA | GFP_KERNEL);
+ idaws = kcalloc(ret, sizeof(*idaws), GFP_DMA | GFP_KERNEL);
if (!idaws) {
- pfn_array_table_unpin_free(pat, cp->mdev);
- return -ENOMEM;
+ ret = -ENOMEM;
+ goto out_unpin;
}
ccw->cda = (__u32) virt_to_phys(idaws);
ccw->flags |= CCW_FLAG_IDA;
@@ -530,6 +531,12 @@ static int ccwchain_fetch_direct(struct ccwchain *chain,
pfn_array_table_idal_create_words(pat, idaws);

return 0;
+
+out_unpin:
+ pfn_array_table_unpin_free(pat, cp->mdev);
+out_init:
+ ccw->cda = 0;
+ return ret;
}

static int ccwchain_fetch_idal(struct ccwchain *chain,
@@ -559,7 +566,7 @@ static int ccwchain_fetch_idal(struct ccwchain *chain,
pat = chain->ch_pat + idx;
ret = pfn_array_table_init(pat, idaw_nr);
if (ret)
- return ret;
+ goto out_init;

/* Translate idal ccw to use new allocated idaws. */
idaws = kzalloc(idaw_len, GFP_DMA | GFP_KERNEL);
@@ -591,6 +598,8 @@ static int ccwchain_fetch_idal(struct ccwchain *chain,
kfree(idaws);
out_unpin:
pfn_array_table_unpin_free(pat, cp->mdev);
+out_init:
+ ccw->cda = 0;
return ret;
}

--
2.13.5