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| author |   Jakub Kicinski <kuba@kernel.org> | 2020-08-10 11:21:11 -0700 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2020-08-10 12:16:51 -0700 |
| commit | 444da3f52407d74c9aa12187ac6b01f76ee47d62 (patch) | |
| tree | 92438be7eb3dfaf7c728361490c91e65367e9985 | |
| parent | tcp: correct read of TFO keys on big endian systems (diff) | |
| download | linux-dev-444da3f52407d74c9aa12187ac6b01f76ee47d62.tar.xz linux-dev-444da3f52407d74c9aa12187ac6b01f76ee47d62.zip | |
bitfield.h: don't compile-time validate _val in FIELD_FIT
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: 1697599ee301a ("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>
| -rw-r--r-- | include/linux/bitfield.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h index 48ea093ff04c..4e035aca6f7e 100644 --- a/include/linux/bitfield.h +++ b/include/linux/bitfield.h @@ -77,7 +77,7 @@ */ #define FIELD_FIT(_mask, _val) \ ({ \ - __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_FIT: "); \ + __BF_FIELD_CHECK(_mask, 0ULL, 0ULL, "FIELD_FIT: "); \ !((((typeof(_mask))_val) << __bf_shf(_mask)) & ~(_mask)); \ }) |