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authorIan Abbott <abbotti@mev.co.uk>2014-10-20 10:10:40 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-10-29 04:18:31 -0400
commit238b5ad855924919e5b98d0c772d9dc78795639b (patch)
tree06c1c2a7cfa0947cfb36155a1b14d42e5a8f6fa3 /drivers/staging
parent0ea6fa037e961dc77cb2bb7a4ad91d172ee4884a (diff)
staging: comedi: fix memory leak / bad pointer freeing for chanlist
As a follow-up to commit 6cab7a37f5c04 ("staging: comedi: (regression) channel list must be set for COMEDI_CMD ioctl"), Hartley Sweeten pointed out another couple of bugs stemming from commit 6cab7a37f5c04 ("staging: comedi: comedi_fops: introduce __comedi_get_user_chanlist()"). Firstly, `do_cmdtest_ioctl()` never frees the kernel copy of the user chanlist allocated by `__comedi_get_user_chanlist()`, so that memory is leaked. Fix it by freeing the allocated kernel memory pointed to by `cmd.chanlist` before that pointer is overwritten with its original pointer to user memory before `cmd` is copied back to user-space. Secondly, if `__comedi_get_user_chanlist()` returns an error, `cmd->chanlist` is left unchanged and in fact will be a pointer to user memory. This causes `do_cmd_ioctl()` to `goto cleanup` and call `do_become_nonbusy()` which would attempt to free the memory pointed to by the user-space pointer. Fix it by setting `cmd->chanlist` to NULL at the start of `__comedi_get_user_chanlist()`. Fixes: c6cd0eefb27b ("staging: comedi: comedi_fops: introduce __comedi_get_user_chanlist()") Reported-by: H Hartley Sweeten <hsweeten@visionengravers.com> Cc: <stable@vger.kernel.org> # 3.15.y 3.16.y 3.17.y: 6cab7a37f5c04 Cc: <stable@vger.kernel.org> # 3.15.y 3.16.y 3.17.y Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/staging')
-rw-r--r--drivers/staging/comedi/comedi_fops.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index f9f61bda92e2..9c32f0276009 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1462,6 +1462,7 @@ static int __comedi_get_user_chanlist(struct comedi_device *dev,
1462 unsigned int *chanlist; 1462 unsigned int *chanlist;
1463 int ret; 1463 int ret;
1464 1464
1465 cmd->chanlist = NULL;
1465 chanlist = memdup_user(user_chanlist, 1466 chanlist = memdup_user(user_chanlist,
1466 cmd->chanlist_len * sizeof(unsigned int)); 1467 cmd->chanlist_len * sizeof(unsigned int));
1467 if (IS_ERR(chanlist)) 1468 if (IS_ERR(chanlist))
@@ -1615,6 +1616,8 @@ static int do_cmdtest_ioctl(struct comedi_device *dev,
1615 1616
1616 ret = s->do_cmdtest(dev, s, &cmd); 1617 ret = s->do_cmdtest(dev, s, &cmd);
1617 1618
1619 kfree(cmd.chanlist); /* free kernel copy of user chanlist */
1620
1618 /* restore chanlist pointer before copying back */ 1621 /* restore chanlist pointer before copying back */
1619 cmd.chanlist = (unsigned int __force *)user_chanlist; 1622 cmd.chanlist = (unsigned int __force *)user_chanlist;
1620 1623