| Message ID | 20200829153515.3840-1-trix@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | soundwire: fix error handling | expand |
On Sat, Aug 29, 2020 at 8:35 AM <trix@redhat.com> wrote: > > From: Tom Rix <trix@redhat.com> > > clang static analysis flags this problem > > stream.c:844:9: warning: Use of memory after > it is freed > kfree(bus->defer_msg.msg->buf); > ^~~~~~~~~~~~~~~~~~~~~~~ > > This happens in an error handler cleaning up memory > allocated for elements in a list. > > list_for_each_entry(m_rt, &stream->master_list, stream_node) { > bus = m_rt->bus; > > kfree(bus->defer_msg.msg->buf); > kfree(bus->defer_msg.msg); > } > > And is triggered when the call to sdw_bank_switch() fails. > There are a two problems. > > First, when sdw_bank_switch() fails, though it frees memory it > does not clear bus's reference 'defer_msg.msg' to that memory. > > The second problem is the freeing msg->buf. In some cases > msg will be NULL so this will dereference a null pointer. > Need to check before freeing. > > Fixes: 99b8a5d608a6 ("soundwire: Add bank switch routine") > Signed-off-by: Tom Rix <trix@redhat.com> > --- > drivers/soundwire/stream.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c > index 37290a799023..6e36deb505b1 100644 > --- a/drivers/soundwire/stream.c > +++ b/drivers/soundwire/stream.c > @@ -717,6 +717,7 @@ static int sdw_bank_switch(struct sdw_bus *bus, int m_rt_count) > kfree(wbuf); > error_1: > kfree(wr_msg); > + bus->defer_msg.msg = NULL; This fix looks correct to me because L668 sets `bus->defer_msg.msg = wr_msg;`, but on error L719 frees `wr_msg`, so now `bus->defer_msg.msg` is a dangling pointer. > return ret; > } > > @@ -840,9 +841,10 @@ static int do_bank_switch(struct sdw_stream_runtime *stream) > error: > list_for_each_entry(m_rt, &stream->master_list, stream_node) { > bus = m_rt->bus; > - > - kfree(bus->defer_msg.msg->buf); > - kfree(bus->defer_msg.msg); > + if (bus->defer_msg.msg) { > + kfree(bus->defer_msg.msg->buf); > + kfree(bus->defer_msg.msg); > + } I'd prefer a conditional check for each, but sdw_ml_sync_bank_switch() has this same pattern, so it looks like the lifetime of these two match. Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Thanks for the patch! > } > > msg_unlock: > -- > 2.18.1 >
On Mon, Aug 31, 2020 at 10:47 AM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Sat, Aug 29, 2020 at 8:35 AM <trix@redhat.com> wrote: > > > > From: Tom Rix <trix@redhat.com> > > > > clang static analysis flags this problem Also, Tom, please use ./scripts/get_maintainer.pl on your patches to CC our mailing list; clang-built-linux@googlegroups.com.
On 8/31/20 10:48 AM, Nick Desaulniers wrote: > On Mon, Aug 31, 2020 at 10:47 AM Nick Desaulniers > <ndesaulniers@google.com> wrote: >> On Sat, Aug 29, 2020 at 8:35 AM <trix@redhat.com> wrote: >>> From: Tom Rix <trix@redhat.com> >>> >>> clang static analysis flags this problem > Also, Tom, please use ./scripts/get_maintainer.pl on your patches to > CC our mailing list; clang-built-linux@googlegroups.com. gcc is still doing the building, so it this appropriate ? Asking because i have been sed-ing clang-build-linux out. Tom
On Mon, Aug 31, 2020 at 11:20 AM Tom Rix <trix@redhat.com> wrote: > > > On 8/31/20 10:48 AM, Nick Desaulniers wrote: > > On Mon, Aug 31, 2020 at 10:47 AM Nick Desaulniers > > <ndesaulniers@google.com> wrote: > >> On Sat, Aug 29, 2020 at 8:35 AM <trix@redhat.com> wrote: > >>> From: Tom Rix <trix@redhat.com> > >>> > >>> clang static analysis flags this problem > > Also, Tom, please use ./scripts/get_maintainer.pl on your patches to > > CC our mailing list; clang-built-linux@googlegroups.com. > > gcc is still doing the building, so it this appropriate ? > > Asking because i have been sed-ing clang-build-linux out. ah, right, you can use `--use-cc=clang` for analyses of builds with clang. It doesn't hurt to include our mailing list, since we'd like to know if issues get reported with the analyzer itself.
On 8/31/20 12:47 PM, Nick Desaulniers wrote: > On Sat, Aug 29, 2020 at 8:35 AM <trix@redhat.com> wrote: >> >> From: Tom Rix <trix@redhat.com> >> >> clang static analysis flags this problem >> >> stream.c:844:9: warning: Use of memory after >> it is freed >> kfree(bus->defer_msg.msg->buf); >> ^~~~~~~~~~~~~~~~~~~~~~~ >> >> This happens in an error handler cleaning up memory >> allocated for elements in a list. >> >> list_for_each_entry(m_rt, &stream->master_list, stream_node) { >> bus = m_rt->bus; >> >> kfree(bus->defer_msg.msg->buf); >> kfree(bus->defer_msg.msg); >> } >> >> And is triggered when the call to sdw_bank_switch() fails. >> There are a two problems. >> >> First, when sdw_bank_switch() fails, though it frees memory it >> does not clear bus's reference 'defer_msg.msg' to that memory. >> >> The second problem is the freeing msg->buf. In some cases >> msg will be NULL so this will dereference a null pointer. >> Need to check before freeing. >> >> Fixes: 99b8a5d608a6 ("soundwire: Add bank switch routine") >> Signed-off-by: Tom Rix <trix@redhat.com> >> --- >> drivers/soundwire/stream.c | 8 +++++--- >> 1 file changed, 5 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c >> index 37290a799023..6e36deb505b1 100644 >> --- a/drivers/soundwire/stream.c >> +++ b/drivers/soundwire/stream.c >> @@ -717,6 +717,7 @@ static int sdw_bank_switch(struct sdw_bus *bus, int m_rt_count) >> kfree(wbuf); >> error_1: >> kfree(wr_msg); >> + bus->defer_msg.msg = NULL; > > This fix looks correct to me because L668 sets `bus->defer_msg.msg = > wr_msg;`, but on error L719 frees `wr_msg`, so now > `bus->defer_msg.msg` is a dangling pointer. > >> return ret; >> } >> >> @@ -840,9 +841,10 @@ static int do_bank_switch(struct sdw_stream_runtime *stream) >> error: >> list_for_each_entry(m_rt, &stream->master_list, stream_node) { >> bus = m_rt->bus; >> - >> - kfree(bus->defer_msg.msg->buf); >> - kfree(bus->defer_msg.msg); >> + if (bus->defer_msg.msg) { >> + kfree(bus->defer_msg.msg->buf); >> + kfree(bus->defer_msg.msg); >> + } > > I'd prefer a conditional check for each, but sdw_ml_sync_bank_switch() > has this same pattern, so it looks like the lifetime of these two > match. > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Also looks good to me. Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
On Tue, Sep 1, 2020 at 4:02 AM Vinod Koul <vkoul@kernel.org> wrote: > > Hello Tom, > > On 29-08-20, 08:35, trix@redhat.com wrote: > > From: Tom Rix <trix@redhat.com> > > > > clang static analysis flags this problem > > > > stream.c:844:9: warning: Use of memory after > > it is freed > > kfree(bus->defer_msg.msg->buf); > > ^~~~~~~~~~~~~~~~~~~~~~~ > > > > This happens in an error handler cleaning up memory > > allocated for elements in a list. > > > > list_for_each_entry(m_rt, &stream->master_list, stream_node) { > > bus = m_rt->bus; > > > > kfree(bus->defer_msg.msg->buf); > > kfree(bus->defer_msg.msg); > > } > > > > And is triggered when the call to sdw_bank_switch() fails. > > There are a two problems. > > > > First, when sdw_bank_switch() fails, though it frees memory it > > does not clear bus's reference 'defer_msg.msg' to that memory. > > > > The second problem is the freeing msg->buf. In some cases > > msg will be NULL so this will dereference a null pointer. > > Need to check before freeing. > > The change looks good to me, but the title of patch should be revised. > > The patch subject should describe the patch, in this case is setting > pointer to null on cleanup, so an appropriate subject may be" > "[PATCH]: soundwire: set defer_msg to null". > > Please revise subject line and update including the ack/reviews > received That's fair, I think soundwire: fix double free of dangling pointer would be most precise.
diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c index 37290a799023..6e36deb505b1 100644 --- a/drivers/soundwire/stream.c +++ b/drivers/soundwire/stream.c @@ -717,6 +717,7 @@ static int sdw_bank_switch(struct sdw_bus *bus, int m_rt_count) kfree(wbuf); error_1: kfree(wr_msg); + bus->defer_msg.msg = NULL; return ret; } @@ -840,9 +841,10 @@ static int do_bank_switch(struct sdw_stream_runtime *stream) error: list_for_each_entry(m_rt, &stream->master_list, stream_node) { bus = m_rt->bus; - - kfree(bus->defer_msg.msg->buf); - kfree(bus->defer_msg.msg); + if (bus->defer_msg.msg) { + kfree(bus->defer_msg.msg->buf); + kfree(bus->defer_msg.msg); + } } msg_unlock: