Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 3.17 271/319] staging: comedi: fix memory leak / bad pointer freeing for chanlist | Date | Wed, 12 Nov 2014 10:16:49 +0900 |
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3.17-stable review patch. If anyone has any objections, please let me know.
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From: Ian Abbott <abbotti@mev.co.uk>
commit 238b5ad855924919e5b98d0c772d9dc78795639b upstream.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/staging/comedi/comedi_fops.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -1462,6 +1462,7 @@ static int __comedi_get_user_chanlist(st 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 comed 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;
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