Messages in this thread Patch in this message | | | From | Ian Abbott <> | Subject | [PATCH] staging: comedi: fix memory leak / bad pointer freeing for chanlist | Date | Mon, 20 Oct 2014 15:10:40 +0100 |
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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 --- Greg, this patch applies to your "staging-linus" branch. --- drivers/staging/comedi/comedi_fops.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index a9b7fe5..a1788e8 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, unsigned int *chanlist; int ret; + cmd->chanlist = NULL; chanlist = memdup_user(user_chanlist, cmd->chanlist_len * sizeof(unsigned int)); if (IS_ERR(chanlist)) @@ -1615,6 +1616,8 @@ static int do_cmdtest_ioctl(struct comedi_device *dev, ret = s->do_cmdtest(dev, s, &cmd); + kfree(cmd.chanlist); /* free kernel copy of user chanlist */ + /* restore chanlist pointer before copying back */ cmd.chanlist = (unsigned int __force *)user_chanlist; -- 2.1.1
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