On Wed, 2019-08-21 at 10:18 +0200, Oliver Neukum wrote: > Am Dienstag, den 20.08.2019, 19:55 +0100 schrieb Ben Hutchings: > > On Tue, 2019-04-30 at 15:07 +0200, Oliver Neukum wrote: > > > dvb_usb_device_exit() frees and uses the device name in that order > > > Fix by storing the name in a buffer before freeing it > > > > > > v2: fixed style issues > > > v3: strscpy used and variable names changed > > > v4: really use strscpy everywhere > > > > > > Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx> > > > Reported-by: syzbot+26ec41e9f788b3eba396@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > This doesn't fix that bug (and I don't think it fixes a bug at all). > > The name string is static and doesn't get freed until the module it's > > in is freed. > > I see. > > > Look again at the stack traces in > > <https://syzkaller.appspot.com/bug?extid=26ec41e9f788b3eba396>;: > > > > > Allocated by task 21: > > > > [...] > > > kmemdup+0x23/0x50 mm/util.c:118 > > > > > > > kmemdup include/linux/string.h:428 [inline] > > > dw2102_probe+0x62c/0xc50 > > > > drivers/media/usb/dvb-usb/dw2102.c:2375 > > [...] > > > Freed by task 21: > > > > [...] > > > > kfree+0xce/0x290 mm/slub.c:3958 > > > dw2102_probe+0x876/0xc50 > > > > drivers/media/usb/dvb-usb/dw2102.c:2409 > > > > So, d->desc was freed during probe, and is a dangling pointer before > > dvb_usb_device_exit() runs at all. > > In that case KASAN would have reported a double free in testing, which > it did not. So far as I could see, the descriptors are normally static data in the driver and nothing in the DVB core frees them. dw2102 is unusual in that it heap-allocated descriptors, which is why this patched fixes a leak: > > The bug seems to have been introduced by: > > > > commit 299c7007e93645067e1d2743f4e50156de78c4ff > > Author: Anton Vasilyev <vasilyev@xxxxxxxxx> > > Date: Mon Jul 23 13:04:54 2018 -0400 > > > > media: dw2102: Fix memleak on sequence of probes > > AFAICT this patch only does anything if probe() succeeds, which it does > not. Something is strange. How did you determine that it doesn't succeed? Ben. -- Ben Hutchings Quantity is no substitute for quality, but it's the only one we've got.
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