On Wed, Feb 08, 2023 at 03:25:53PM -0800, Kees Cook wrote: > Clang can do some aggressive inlining, which provides it with greater > visibility into the sizes of various objects that are passed into > helpers. Specifically, compare_netdev_and_ip() can see through the type > given to the "sa" argument, which means it can generate code for "struct > sockaddr_in" that would have been passed to ipv6_addr_cmp() (that expects > to operate on the larger "struct sockaddr_in6"), which would result in a > compile-time buffer overflow condition detected by memcmp(). Logically, > this state isn't reachable due to the sa_family assignment two callers > above and the check in compare_netdev_and_ip(). Instead, provide a > compile-time check on sizes so the size-mismatched code will be elided > when inlining. Avoids the following warning from Clang: > > ../include/linux/fortify-string.h:652:4: error: call to '__read_overflow' declared with 'error' attribute: detected read beyond size of object (1st parameter) > __read_overflow(); > ^ > note: In function 'cma_netevent_callback' > note: which inlined function 'node_from_ndev_ip' > 1 error generated. > > When the underlying object size is not known (e.g. with GCC and older > Clang), the result of __builtin_object_size() is SIZE_MAX, which > will also compile away, leaving the code as it was originally. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1687 > Cc: Jason Gunthorpe <jgg@xxxxxxxx> > Cc: Leon Romanovsky <leon@xxxxxxxxxx> > Cc: Mark Zhang <markzhang@xxxxxxxxxx> > Cc: Patrisious Haddad <phaddad@xxxxxxxxxx> > Cc: Nathan Chancellor <nathan@xxxxxxxxxx> > Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > Cc: linux-rdma@xxxxxxxxxxxxxxx > Cc: llvm@xxxxxxxxxxxxxxx > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx> # build Should this have a 'Cc: stable@xxxxxxxxxxxxxxx', since we see this in 6.1? > --- > drivers/infiniband/core/cma.c | 17 ++++++++++++----- > 1 file changed, 12 insertions(+), 5 deletions(-) > > diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c > index 1d2bff91d78b..308155937713 100644 > --- a/drivers/infiniband/core/cma.c > +++ b/drivers/infiniband/core/cma.c > @@ -479,13 +479,20 @@ static int compare_netdev_and_ip(int ifindex_a, struct sockaddr *sa, > if (sa->sa_family != sb->sa_family) > return sa->sa_family - sb->sa_family; > > - if (sa->sa_family == AF_INET) > - return memcmp((char *)&((struct sockaddr_in *)sa)->sin_addr, > - (char *)&((struct sockaddr_in *)sb)->sin_addr, > + if (sa->sa_family == AF_INET && > + __builtin_object_size(sa, 0) >= sizeof(struct sockaddr_in)) { > + return memcmp(&((struct sockaddr_in *)sa)->sin_addr, > + &((struct sockaddr_in *)sb)->sin_addr, > sizeof(((struct sockaddr_in *)sa)->sin_addr)); > + } > + > + if (sa->sa_family == AF_INET6 && > + __builtin_object_size(sa, 0) >= sizeof(struct sockaddr_in6)) { > + return ipv6_addr_cmp(&((struct sockaddr_in6 *)sa)->sin6_addr, > + &((struct sockaddr_in6 *)sb)->sin6_addr); > + } > > - return ipv6_addr_cmp(&((struct sockaddr_in6 *)sa)->sin6_addr, > - &((struct sockaddr_in6 *)sb)->sin6_addr); > + return -1; > } > > static int cma_add_id_to_tree(struct rdma_id_private *node_id_priv) > -- > 2.34.1 >
