commit 444da3f524 upstream.
When ur_load_imm_any() is inlined into jeq_imm(), it's possible for the
compiler to deduce a case where _val can only have the value of -1 at
compile time. Specifically,
/* struct bpf_insn: _s32 imm */
u64 imm = insn->imm; /* sign extend */
if (imm >> 32) { /* non-zero only if insn->imm is negative */
/* inlined from ur_load_imm_any */
u32 __imm = imm >> 32; /* therefore, always 0xffffffff */
if (__builtin_constant_p(__imm) && __imm > 255)
compiletime_assert_XXX()
This can result in tripping a BUILD_BUG_ON() in __BF_FIELD_CHECK() that
checks that a given value is representable in one byte (interpreted as
unsigned).
FIELD_FIT() should return true or false at runtime for whether a value
can fit for not. Don't break the build over a value that's too large for
the mask. We'd prefer to keep the inlining and compiler optimizations
though we know this case will always return false.
Cc: stable@vger.kernel.org
Fixes: 1697599ee3 ("bitfield.h: add FIELD_FIT() helper")
Link: https://lore.kernel.org/kernel-hardening/CAK7LNASvb0UDJ0U5wkYYRzTAdnEs64HjXpEUL7d=V0CXiAXcNw@mail.gmail.com/
Reported-by: Masahiro Yamada <masahiroy@kernel.org>
Debugged-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2824988a20