Commit 9bf4e919ccad worked around an issue introduced after an innocuous optimisation change in LLVM main: > len is defined as an 'int' because it is assigned from > '__user int *optlen'. However, it is clamped against the result of > sizeof(), which has a type of 'size_t' ('unsigned long' for 64-bit > platforms). This is done with min_t() because min() requires compatible > types, which results in both len and the result of sizeof() being casted > to 'unsigned int', meaning len changes signs and the result of sizeof() > is truncated. From there, len is passed to copy_to_user(), which has a > third parameter type of 'unsigned long', so it is widened and changes > signs again. This excessive casting in combination with the KCSAN > instrumentation causes LLVM to fail to eliminate the __bad_copy_from() > call, failing the build. The same issue occurs in rfcomm in functions rfcomm_sock_bind and rfcomm_sock_getsockopt_old. Change the type of len to size_t in both rfcomm_sock_bind and rfcomm_sock_getsockopt_old and replace min_t() with min(). Cc: stable@xxxxxxxxxxxxxxx Fixes: 9bf4e919ccad ("Bluetooth: Fix type of len in {l2cap,sco}_sock_getsockopt_old()") Link: https://github.com/ClangBuiltLinux/linux/issues/2007 Link: https://github.com/llvm/llvm-project/issues/85647 Signed-off-by: Andrej Shadura <andrew.shadura@xxxxxxxxxxxxxxx> --- net/bluetooth/rfcomm/sock.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c index 37d63d768afb..c0fe96673b3c 100644 --- a/net/bluetooth/rfcomm/sock.c +++ b/net/bluetooth/rfcomm/sock.c @@ -328,14 +328,15 @@ static int rfcomm_sock_bind(struct socket *sock, struct sockaddr *addr, int addr { struct sockaddr_rc sa; struct sock *sk = sock->sk; - int len, err = 0; + int err = 0; + size_t len; if (!addr || addr_len < offsetofend(struct sockaddr, sa_family) || addr->sa_family != AF_BLUETOOTH) return -EINVAL; memset(&sa, 0, sizeof(sa)); - len = min_t(unsigned int, sizeof(sa), addr_len); + len = min(sizeof(sa), addr_len); memcpy(&sa, addr, len); BT_DBG("sk %p %pMR", sk, &sa.rc_bdaddr); @@ -729,7 +730,8 @@ static int rfcomm_sock_getsockopt_old(struct socket *sock, int optname, char __u struct sock *l2cap_sk; struct l2cap_conn *conn; struct rfcomm_conninfo cinfo; - int len, err = 0; + int err = 0; + size_t len; u32 opt; BT_DBG("sk %p", sk); @@ -783,7 +785,7 @@ static int rfcomm_sock_getsockopt_old(struct socket *sock, int optname, char __u cinfo.hci_handle = conn->hcon->handle; memcpy(cinfo.dev_class, conn->hcon->dev_class, 3); - len = min_t(unsigned int, len, sizeof(cinfo)); + len = min(len, sizeof(cinfo)); if (copy_to_user(optval, (char *) &cinfo, len)) err = -EFAULT; -- 2.43.0