First, please fix your patch Subject which is way too verbose. You should aim at less than 72 chars including prefix. Something like "vt: keyboard: suppress smatch warning in vt_do_kdgkb_ioctl" should do. On Sun, Nov 07, 2021 at 08:47:21AM +0530, Ajay Garg wrote: > smatch-kchecker gives the following warnings when run on keyboard.c : > > vt_do_kdgkb_ioctl() error: uninitialized symbol 'kbs'. > vt_do_kdgkb_ioctl() error: uninitialized symbol 'ret'. > > This usually happens when switch has no default case and static > analyzers and even sometimes compilers can’t prove that all possible > values are covered. > > Thus, the default switch-case has been added, which sets the values > for the two variables : > > * kbs as NULL, which also nicely fits in with kfree. > > * ret as -ENOIOCTLCMD (on same lines if there is no cmd > match in "vt_do_kdskled" method). Not sure how far we want to take the suppression of false-positive warnings but at least this isn't the right way to do it. > Many thanks to the following for review of previous versions : > > * Pavel Skripkin <paskripkin@xxxxxxxxx> > * Andy Shevchenko <andy.shevchenko@xxxxxxxxx> > > > Signed-off-by: Ajay Garg <ajaygargnsit@xxxxxxxxx> > --- > > > There were discussions previously, and the current patch is the > result. > > v1 : > https://lore.kernel.org/linux-serial/YYZN30qfaKMskVwE@xxxxxxxxx/T/#t > > v2 : > https://lore.kernel.org/linux-serial/CAHP4M8Vdj4Eb8q773BeHvsW9n6t=3n1WznuXAR4fZCNi1J6rOg@xxxxxxxxxxxxxx/T/#m18f45676feaba6b1f01ddd5fe607997b190ef4b9 > > v3 : > https://lore.kernel.org/linux-serial/20211106220315.392842-1-ajaygargnsit@xxxxxxxxx/T/#u > > Changes in v2 : > > * Changes as required by scripts/checkpatch.pl > > * Checking whether kbs is not NULL before kfree is not required, > as kfree(NULL) is safe. So, dropped the check. > > Changes in v3 : > > * Using default-switch case, and setting the variables > when there is no matching cmd. > > Changes in v4 : > > * Removed braces for the default switch-case. > > > drivers/tty/vt/keyboard.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > > diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c > index c7fbbcdcc346..f66c32fe7ef1 100644 > --- a/drivers/tty/vt/keyboard.c > +++ b/drivers/tty/vt/keyboard.c > @@ -2090,6 +2090,10 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm) > > ret = 0; > break; > + default: > + kbs = NULL; > + ret = -ENOIOCTLCMD; > + break; > } > > kfree(kbs); Instead, move the kfree() into the two cases blocks and initialise ret to 0 as is done in several other vt helpers in case a driver bug ever causes them to be called for the wrong cmds (e.g. instead of sprinkling WARN_ON(1) in all those functions). You may want to mention that the kfree warning was introduced by 07edff926520 ("vt: keyboard, reorder user buffer handling in vt_do_kdgkb_ioctl") which moved the shared allocation into the switch statement, and perhaps also mention 4e1404a5cd04 ("vt: keyboard, extract and simplify vt_kdskbsent") for the ret warning. Johan
