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authorJakub Kicinski <kuba@kernel.org>2020-08-10 21:21:11 +0300
committerDavid S. Miller <davem@davemloft.net>2020-08-10 22:16:51 +0300
commit444da3f52407d74c9aa12187ac6b01f76ee47d62 (patch)
tree92438be7eb3dfaf7c728361490c91e65367e9985 /include/linux/bitfield.h
parentf19008e676366c44e9241af57f331b6c6edf9552 (diff)
downloadlinux-444da3f52407d74c9aa12187ac6b01f76ee47d62.tar.xz
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>
Diffstat (limited to 'include/linux/bitfield.h')
-rw-r--r--include/linux/bitfield.h2
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)); \
})