On Thu, Jun 1, 2017 at 4:04 PM, Yury Norov <yno...@caviumnetworks.com> wrote: > On Thu, Jun 01, 2017 at 03:50:33PM +0200, Alexander Potapenko wrote: >> On Thu, Jun 1, 2017 at 3:47 PM, Yury Norov <yno...@caviumnetworks.com> wrote: >> > On Thu, Jun 01, 2017 at 02:38:29PM +0200, Alexander Potapenko wrote: >> >> KMSAN reported a use of uninitialized memory in dev_set_alias(), >> >> which was caused by calling strlcpy() (which in turn called strlen()) >> >> on the user-supplied non-terminated string. >> >> >> >> Signed-off-by: Alexander Potapenko <gli...@google.com> >> >> --- >> >> v3: removed the multi-line comment >> >> v2: fixed an off-by-one error spotted by Dmitry Vyukov >> > >> > [...] >> > >> >> --- >> >> net/core/dev.c | 4 +++- >> >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> >> >> diff --git a/net/core/dev.c b/net/core/dev.c >> >> index fca407b4a6ea..3e3b29133cc9 100644 >> >> --- a/net/core/dev.c >> >> +++ b/net/core/dev.c >> >> @@ -1254,7 +1254,9 @@ int dev_set_alias(struct net_device *dev, const >> >> char *alias, size_t len) >> >> return -ENOMEM; >> >> dev->ifalias = new_ifalias; >> >> >> >> - strlcpy(dev->ifalias, alias, len+1); >> >> + /* alias comes from the userspace and may not be zero-terminated. */ >> > >> > So if the comment is correct, you'd use copy_from_user() instead. >> Well, the contents of |alias| have been previously copied from the >> userspace, but this is a pointer to a kernel buffer, as the function >> prototype tells. >> Do you think a confusion is possible here? > > Yes, I think so... If pointer comes from userspace, it normally points to > userspace data. If you have the data already copied, just say: > + /* alias may not be zero-terminated. */ > > Or say nothing, because at the first glance, using the strlcpy() > instead of simple memcpy() looks weird in this case - you know the > length of the string from the beginning, and should not recalculate it > again. You're right, I'll just drop this line. > Yury > >> >> + memcpy(dev->ifalias, alias, len); >> >> + dev->ifalias[len] = 0; >> >> return len; >> >> } >> >> >> >> -- >> >> 2.13.0.219.gdb65acc882-goog >> >> >> >> -- >> Alexander Potapenko >> Software Engineer >> >> Google Germany GmbH >> Erika-Mann-Straße, 33 >> 80636 München >> >> Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle >> Registergericht und -nummer: Hamburg, HRB 86891 >> Sitz der Gesellschaft: Hamburg
-- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
