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 > --- > drivers/infiniband/core/cma.c | 17 ++++++++++++----- > 1 file changed, 12 insertions(+), 5 deletions(-) This seems hacky, but I guess I can see why it is unreasonable for the compiler to track the sa_family in this case. Applied to for next Jason
