| Message ID | 20220124192849.14755-1-Jason@zx2c4.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] lib/crypto: blake2s: avoid indirect calls to compression function for Clang CFI | expand |
On Mon, Jan 24, 2022 at 11:29 AM Jason A. Donenfeld <Jason@zx2c4.com> wrote: > > blake2s_compress_generic is weakly aliased by blake2s_generic. The > current harness for function selection uses a function pointer, which is > ordinarily inlined and resolved at compile time. But when Clang's CFI is > enabled, CFI still triggers when making an indirect call via a weak > symbol. This seems like a bug in Clang's CFI, as though it's bucketing > weak symbols and strong symbols differently. It also only seems to > trigger when "full LTO" mode is used, rather than "thin LTO". > > [ 0.000000][ T0] Kernel panic - not syncing: CFI failure (target: blake2s_compress_generic+0x0/0x1444) > [ 0.000000][ T0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.16.0-mainline-06981-g076c855b846e #1 > [ 0.000000][ T0] Hardware name: MT6873 (DT) > [ 0.000000][ T0] Call trace: > [ 0.000000][ T0] dump_backtrace+0xfc/0x1dc > [ 0.000000][ T0] dump_stack_lvl+0xa8/0x11c > [ 0.000000][ T0] panic+0x194/0x464 > [ 0.000000][ T0] __cfi_check_fail+0x54/0x58 > [ 0.000000][ T0] __cfi_slowpath_diag+0x354/0x4b0 > [ 0.000000][ T0] blake2s_update+0x14c/0x178 > [ 0.000000][ T0] _extract_entropy+0xf4/0x29c > [ 0.000000][ T0] crng_initialize_primary+0x24/0x94 > [ 0.000000][ T0] rand_initialize+0x2c/0x6c > [ 0.000000][ T0] start_kernel+0x2f8/0x65c > [ 0.000000][ T0] __primary_switched+0xc4/0x7be4 > [ 0.000000][ T0] Rebooting in 5 seconds.. > > Nonetheless, the function pointer method isn't so terrific anyway, so > this patch replaces it with a simple boolean, which also gets inlined > away. This successfully works around the Clang bug. Acked-by: Nick Desaulniers <ndesaulniers@google.com> Thanks for the report. Once we have a fix in hand for LLVM, we can revisit removing this and raising the required LLVM version for CFI. > > In general, I'm not too keen on all of the indirection involved here; it > clearly does more harm than good. Hopefully the whole thing can get > cleaned up down the road when lib/crypto is overhauled more > comprehensively. But for now, we go with a simple bandaid. > > Fixes: 6048fdcc5f26 ("lib/crypto: blake2s: include as built-in") > Reported-by: Miles Chen <miles.chen@mediatek.com> > Tested-by: Miles Chen <miles.chen@mediatek.com> > Tested-by: Nathan Chancellor <nathan@kernel.org> > Link: https://github.com/ClangBuiltLinux/linux/issues/1567 > Cc: Nick Desaulniers <ndesaulniers@google.com> > Cc: Sami Tolvanen <samitolvanen@google.com> > Cc: Ard Biesheuvel <ardb@kernel.org> > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> > --- > Changes v1->v2: > - Wrapped columns at 80 for Eric. > > arch/arm/crypto/blake2s-shash.c | 4 ++-- > arch/x86/crypto/blake2s-shash.c | 4 ++-- > crypto/blake2s_generic.c | 4 ++-- > include/crypto/internal/blake2s.h | 40 +++++++++++++++++++------------ > lib/crypto/blake2s.c | 4 ++-- > 5 files changed, 33 insertions(+), 23 deletions(-) > > diff --git a/arch/arm/crypto/blake2s-shash.c b/arch/arm/crypto/blake2s-shash.c > index 17c1c3bfe2f5..763c73beea2d 100644 > --- a/arch/arm/crypto/blake2s-shash.c > +++ b/arch/arm/crypto/blake2s-shash.c > @@ -13,12 +13,12 @@ > static int crypto_blake2s_update_arm(struct shash_desc *desc, > const u8 *in, unsigned int inlen) > { > - return crypto_blake2s_update(desc, in, inlen, blake2s_compress); > + return crypto_blake2s_update(desc, in, inlen, false); > } > > static int crypto_blake2s_final_arm(struct shash_desc *desc, u8 *out) > { > - return crypto_blake2s_final(desc, out, blake2s_compress); > + return crypto_blake2s_final(desc, out, false); > } > > #define BLAKE2S_ALG(name, driver_name, digest_size) \ > diff --git a/arch/x86/crypto/blake2s-shash.c b/arch/x86/crypto/blake2s-shash.c > index f9e2fecdb761..59ae28abe35c 100644 > --- a/arch/x86/crypto/blake2s-shash.c > +++ b/arch/x86/crypto/blake2s-shash.c > @@ -18,12 +18,12 @@ > static int crypto_blake2s_update_x86(struct shash_desc *desc, > const u8 *in, unsigned int inlen) > { > - return crypto_blake2s_update(desc, in, inlen, blake2s_compress); > + return crypto_blake2s_update(desc, in, inlen, false); > } > > static int crypto_blake2s_final_x86(struct shash_desc *desc, u8 *out) > { > - return crypto_blake2s_final(desc, out, blake2s_compress); > + return crypto_blake2s_final(desc, out, false); > } > > #define BLAKE2S_ALG(name, driver_name, digest_size) \ > diff --git a/crypto/blake2s_generic.c b/crypto/blake2s_generic.c > index 72fe480f9bd6..5f96a21f8788 100644 > --- a/crypto/blake2s_generic.c > +++ b/crypto/blake2s_generic.c > @@ -15,12 +15,12 @@ > static int crypto_blake2s_update_generic(struct shash_desc *desc, > const u8 *in, unsigned int inlen) > { > - return crypto_blake2s_update(desc, in, inlen, blake2s_compress_generic); > + return crypto_blake2s_update(desc, in, inlen, true); > } > > static int crypto_blake2s_final_generic(struct shash_desc *desc, u8 *out) > { > - return crypto_blake2s_final(desc, out, blake2s_compress_generic); > + return crypto_blake2s_final(desc, out, true); > } > > #define BLAKE2S_ALG(name, driver_name, digest_size) \ > diff --git a/include/crypto/internal/blake2s.h b/include/crypto/internal/blake2s.h > index d39cfa0d333e..52363eee2b20 100644 > --- a/include/crypto/internal/blake2s.h > +++ b/include/crypto/internal/blake2s.h > @@ -24,14 +24,11 @@ static inline void blake2s_set_lastblock(struct blake2s_state *state) > state->f[0] = -1; > } > > -typedef void (*blake2s_compress_t)(struct blake2s_state *state, > - const u8 *block, size_t nblocks, u32 inc); > - > /* Helper functions for BLAKE2s shared by the library and shash APIs */ > > -static inline void __blake2s_update(struct blake2s_state *state, > - const u8 *in, size_t inlen, > - blake2s_compress_t compress) > +static __always_inline void > +__blake2s_update(struct blake2s_state *state, const u8 *in, size_t inlen, > + bool force_generic) > { > const size_t fill = BLAKE2S_BLOCK_SIZE - state->buflen; > > @@ -39,7 +36,12 @@ static inline void __blake2s_update(struct blake2s_state *state, > return; > if (inlen > fill) { > memcpy(state->buf + state->buflen, in, fill); > - (*compress)(state, state->buf, 1, BLAKE2S_BLOCK_SIZE); > + if (force_generic) > + blake2s_compress_generic(state, state->buf, 1, > + BLAKE2S_BLOCK_SIZE); > + else > + blake2s_compress(state, state->buf, 1, > + BLAKE2S_BLOCK_SIZE); > state->buflen = 0; > in += fill; > inlen -= fill; > @@ -47,7 +49,12 @@ static inline void __blake2s_update(struct blake2s_state *state, > if (inlen > BLAKE2S_BLOCK_SIZE) { > const size_t nblocks = DIV_ROUND_UP(inlen, BLAKE2S_BLOCK_SIZE); > /* Hash one less (full) block than strictly possible */ > - (*compress)(state, in, nblocks - 1, BLAKE2S_BLOCK_SIZE); > + if (force_generic) > + blake2s_compress_generic(state, in, nblocks - 1, > + BLAKE2S_BLOCK_SIZE); > + else > + blake2s_compress(state, in, nblocks - 1, > + BLAKE2S_BLOCK_SIZE); > in += BLAKE2S_BLOCK_SIZE * (nblocks - 1); > inlen -= BLAKE2S_BLOCK_SIZE * (nblocks - 1); > } > @@ -55,13 +62,16 @@ static inline void __blake2s_update(struct blake2s_state *state, > state->buflen += inlen; > } > > -static inline void __blake2s_final(struct blake2s_state *state, u8 *out, > - blake2s_compress_t compress) > +static __always_inline void > +__blake2s_final(struct blake2s_state *state, u8 *out, bool force_generic) > { > blake2s_set_lastblock(state); > memset(state->buf + state->buflen, 0, > BLAKE2S_BLOCK_SIZE - state->buflen); /* Padding */ > - (*compress)(state, state->buf, 1, state->buflen); > + if (force_generic) > + blake2s_compress_generic(state, state->buf, 1, state->buflen); > + else > + blake2s_compress(state, state->buf, 1, state->buflen); > cpu_to_le32_array(state->h, ARRAY_SIZE(state->h)); > memcpy(out, state->h, state->outlen); > } > @@ -99,20 +109,20 @@ static inline int crypto_blake2s_init(struct shash_desc *desc) > > static inline int crypto_blake2s_update(struct shash_desc *desc, > const u8 *in, unsigned int inlen, > - blake2s_compress_t compress) > + bool force_generic) > { > struct blake2s_state *state = shash_desc_ctx(desc); > > - __blake2s_update(state, in, inlen, compress); > + __blake2s_update(state, in, inlen, force_generic); > return 0; > } > > static inline int crypto_blake2s_final(struct shash_desc *desc, u8 *out, > - blake2s_compress_t compress) > + bool force_generic) > { > struct blake2s_state *state = shash_desc_ctx(desc); > > - __blake2s_final(state, out, compress); > + __blake2s_final(state, out, force_generic); > return 0; > } > > diff --git a/lib/crypto/blake2s.c b/lib/crypto/blake2s.c > index 9364f79937b8..c71c09621c09 100644 > --- a/lib/crypto/blake2s.c > +++ b/lib/crypto/blake2s.c > @@ -18,14 +18,14 @@ > > void blake2s_update(struct blake2s_state *state, const u8 *in, size_t inlen) > { > - __blake2s_update(state, in, inlen, blake2s_compress); > + __blake2s_update(state, in, inlen, false); > } > EXPORT_SYMBOL(blake2s_update); > > void blake2s_final(struct blake2s_state *state, u8 *out) > { > WARN_ON(IS_ENABLED(DEBUG) && !out); > - __blake2s_final(state, out, blake2s_compress); > + __blake2s_final(state, out, false); > memzero_explicit(state, sizeof(*state)); > } > EXPORT_SYMBOL(blake2s_final); > -- > 2.34.1 >
On Mon, Jan 24, 2022 at 08:28:49PM +0100, Jason A. Donenfeld wrote: > blake2s_compress_generic is weakly aliased by blake2s_generic. The Don't you mean "weakly aliased by blake2s_compress"? > Fixes: 6048fdcc5f26 ("lib/crypto: blake2s: include as built-in") > Reported-by: Miles Chen <miles.chen@mediatek.com> > Tested-by: Miles Chen <miles.chen@mediatek.com> > Tested-by: Nathan Chancellor <nathan@kernel.org> > Link: https://github.com/ClangBuiltLinux/linux/issues/1567 > Cc: Nick Desaulniers <ndesaulniers@google.com> > Cc: Sami Tolvanen <samitolvanen@google.com> > Cc: Ard Biesheuvel <ardb@kernel.org> > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> > --- Otherwise this looks fine, though it's unfortunate this is needed. You can add: Reviewed-by: Eric Biggers <ebiggers@google.com> > Changes v1->v2: > - Wrapped columns at 80 for Eric. It is the recommended coding style, so not just for me :-) - Eric
On 1/25/22, Eric Biggers <ebiggers@kernel.org> wrote: > On Mon, Jan 24, 2022 at 08:28:49PM +0100, Jason A. Donenfeld wrote: >> blake2s_compress_generic is weakly aliased by blake2s_generic. The > > Don't you mean "weakly aliased by blake2s_compress"? Grrrr. Thanks. >> Changes v1->v2: >> - Wrapped columns at 80 for Eric. > > It is the recommended coding style, so not just for me :-) I was under the impression this increased to 100 mid-2020 or so, and checkpatch.pl now makes noise at that width instead.
On Tue, Jan 25, 2022 at 01:23:34PM +0100, Jason A. Donenfeld wrote: > On 1/25/22, Eric Biggers <ebiggers@kernel.org> wrote: > > On Mon, Jan 24, 2022 at 08:28:49PM +0100, Jason A. Donenfeld wrote: > >> blake2s_compress_generic is weakly aliased by blake2s_generic. The > > > > Don't you mean "weakly aliased by blake2s_compress"? > > Grrrr. Thanks. > > >> Changes v1->v2: > >> - Wrapped columns at 80 for Eric. > > > > It is the recommended coding style, so not just for me :-) > > I was under the impression this increased to 100 mid-2020 or so, and > checkpatch.pl now makes noise at that width instead. From Documentation/process/coding-style.rst: "The preferred limit on the length of a single line is 80 columns. Statements longer than 80 columns should be broken into sensible chunks, unless exceeding 80 columns significantly increases readability and does not hide information." It's not as strict as it used to be, but checkpatch seems to be overly-lenient. I always run it with --max-line-length=80. - Eric
diff --git a/arch/arm/crypto/blake2s-shash.c b/arch/arm/crypto/blake2s-shash.c index 17c1c3bfe2f5..763c73beea2d 100644 --- a/arch/arm/crypto/blake2s-shash.c +++ b/arch/arm/crypto/blake2s-shash.c @@ -13,12 +13,12 @@ static int crypto_blake2s_update_arm(struct shash_desc *desc, const u8 *in, unsigned int inlen) { - return crypto_blake2s_update(desc, in, inlen, blake2s_compress); + return crypto_blake2s_update(desc, in, inlen, false); } static int crypto_blake2s_final_arm(struct shash_desc *desc, u8 *out) { - return crypto_blake2s_final(desc, out, blake2s_compress); + return crypto_blake2s_final(desc, out, false); } #define BLAKE2S_ALG(name, driver_name, digest_size) \ diff --git a/arch/x86/crypto/blake2s-shash.c b/arch/x86/crypto/blake2s-shash.c index f9e2fecdb761..59ae28abe35c 100644 --- a/arch/x86/crypto/blake2s-shash.c +++ b/arch/x86/crypto/blake2s-shash.c @@ -18,12 +18,12 @@ static int crypto_blake2s_update_x86(struct shash_desc *desc, const u8 *in, unsigned int inlen) { - return crypto_blake2s_update(desc, in, inlen, blake2s_compress); + return crypto_blake2s_update(desc, in, inlen, false); } static int crypto_blake2s_final_x86(struct shash_desc *desc, u8 *out) { - return crypto_blake2s_final(desc, out, blake2s_compress); + return crypto_blake2s_final(desc, out, false); } #define BLAKE2S_ALG(name, driver_name, digest_size) \ diff --git a/crypto/blake2s_generic.c b/crypto/blake2s_generic.c index 72fe480f9bd6..5f96a21f8788 100644 --- a/crypto/blake2s_generic.c +++ b/crypto/blake2s_generic.c @@ -15,12 +15,12 @@ static int crypto_blake2s_update_generic(struct shash_desc *desc, const u8 *in, unsigned int inlen) { - return crypto_blake2s_update(desc, in, inlen, blake2s_compress_generic); + return crypto_blake2s_update(desc, in, inlen, true); } static int crypto_blake2s_final_generic(struct shash_desc *desc, u8 *out) { - return crypto_blake2s_final(desc, out, blake2s_compress_generic); + return crypto_blake2s_final(desc, out, true); } #define BLAKE2S_ALG(name, driver_name, digest_size) \ diff --git a/include/crypto/internal/blake2s.h b/include/crypto/internal/blake2s.h index d39cfa0d333e..52363eee2b20 100644 --- a/include/crypto/internal/blake2s.h +++ b/include/crypto/internal/blake2s.h @@ -24,14 +24,11 @@ static inline void blake2s_set_lastblock(struct blake2s_state *state) state->f[0] = -1; } -typedef void (*blake2s_compress_t)(struct blake2s_state *state, - const u8 *block, size_t nblocks, u32 inc); - /* Helper functions for BLAKE2s shared by the library and shash APIs */ -static inline void __blake2s_update(struct blake2s_state *state, - const u8 *in, size_t inlen, - blake2s_compress_t compress) +static __always_inline void +__blake2s_update(struct blake2s_state *state, const u8 *in, size_t inlen, + bool force_generic) { const size_t fill = BLAKE2S_BLOCK_SIZE - state->buflen; @@ -39,7 +36,12 @@ static inline void __blake2s_update(struct blake2s_state *state, return; if (inlen > fill) { memcpy(state->buf + state->buflen, in, fill); - (*compress)(state, state->buf, 1, BLAKE2S_BLOCK_SIZE); + if (force_generic) + blake2s_compress_generic(state, state->buf, 1, + BLAKE2S_BLOCK_SIZE); + else + blake2s_compress(state, state->buf, 1, + BLAKE2S_BLOCK_SIZE); state->buflen = 0; in += fill; inlen -= fill; @@ -47,7 +49,12 @@ static inline void __blake2s_update(struct blake2s_state *state, if (inlen > BLAKE2S_BLOCK_SIZE) { const size_t nblocks = DIV_ROUND_UP(inlen, BLAKE2S_BLOCK_SIZE); /* Hash one less (full) block than strictly possible */ - (*compress)(state, in, nblocks - 1, BLAKE2S_BLOCK_SIZE); + if (force_generic) + blake2s_compress_generic(state, in, nblocks - 1, + BLAKE2S_BLOCK_SIZE); + else + blake2s_compress(state, in, nblocks - 1, + BLAKE2S_BLOCK_SIZE); in += BLAKE2S_BLOCK_SIZE * (nblocks - 1); inlen -= BLAKE2S_BLOCK_SIZE * (nblocks - 1); } @@ -55,13 +62,16 @@ static inline void __blake2s_update(struct blake2s_state *state, state->buflen += inlen; } -static inline void __blake2s_final(struct blake2s_state *state, u8 *out, - blake2s_compress_t compress) +static __always_inline void +__blake2s_final(struct blake2s_state *state, u8 *out, bool force_generic) { blake2s_set_lastblock(state); memset(state->buf + state->buflen, 0, BLAKE2S_BLOCK_SIZE - state->buflen); /* Padding */ - (*compress)(state, state->buf, 1, state->buflen); + if (force_generic) + blake2s_compress_generic(state, state->buf, 1, state->buflen); + else + blake2s_compress(state, state->buf, 1, state->buflen); cpu_to_le32_array(state->h, ARRAY_SIZE(state->h)); memcpy(out, state->h, state->outlen); } @@ -99,20 +109,20 @@ static inline int crypto_blake2s_init(struct shash_desc *desc) static inline int crypto_blake2s_update(struct shash_desc *desc, const u8 *in, unsigned int inlen, - blake2s_compress_t compress) + bool force_generic) { struct blake2s_state *state = shash_desc_ctx(desc); - __blake2s_update(state, in, inlen, compress); + __blake2s_update(state, in, inlen, force_generic); return 0; } static inline int crypto_blake2s_final(struct shash_desc *desc, u8 *out, - blake2s_compress_t compress) + bool force_generic) { struct blake2s_state *state = shash_desc_ctx(desc); - __blake2s_final(state, out, compress); + __blake2s_final(state, out, force_generic); return 0; } diff --git a/lib/crypto/blake2s.c b/lib/crypto/blake2s.c index 9364f79937b8..c71c09621c09 100644 --- a/lib/crypto/blake2s.c +++ b/lib/crypto/blake2s.c @@ -18,14 +18,14 @@ void blake2s_update(struct blake2s_state *state, const u8 *in, size_t inlen) { - __blake2s_update(state, in, inlen, blake2s_compress); + __blake2s_update(state, in, inlen, false); } EXPORT_SYMBOL(blake2s_update); void blake2s_final(struct blake2s_state *state, u8 *out) { WARN_ON(IS_ENABLED(DEBUG) && !out); - __blake2s_final(state, out, blake2s_compress); + __blake2s_final(state, out, false); memzero_explicit(state, sizeof(*state)); } EXPORT_SYMBOL(blake2s_final);
blake2s_compress_generic is weakly aliased by blake2s_generic. The current harness for function selection uses a function pointer, which is ordinarily inlined and resolved at compile time. But when Clang's CFI is enabled, CFI still triggers when making an indirect call via a weak symbol. This seems like a bug in Clang's CFI, as though it's bucketing weak symbols and strong symbols differently. It also only seems to trigger when "full LTO" mode is used, rather than "thin LTO". [ 0.000000][ T0] Kernel panic - not syncing: CFI failure (target: blake2s_compress_generic+0x0/0x1444) [ 0.000000][ T0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.16.0-mainline-06981-g076c855b846e #1 [ 0.000000][ T0] Hardware name: MT6873 (DT) [ 0.000000][ T0] Call trace: [ 0.000000][ T0] dump_backtrace+0xfc/0x1dc [ 0.000000][ T0] dump_stack_lvl+0xa8/0x11c [ 0.000000][ T0] panic+0x194/0x464 [ 0.000000][ T0] __cfi_check_fail+0x54/0x58 [ 0.000000][ T0] __cfi_slowpath_diag+0x354/0x4b0 [ 0.000000][ T0] blake2s_update+0x14c/0x178 [ 0.000000][ T0] _extract_entropy+0xf4/0x29c [ 0.000000][ T0] crng_initialize_primary+0x24/0x94 [ 0.000000][ T0] rand_initialize+0x2c/0x6c [ 0.000000][ T0] start_kernel+0x2f8/0x65c [ 0.000000][ T0] __primary_switched+0xc4/0x7be4 [ 0.000000][ T0] Rebooting in 5 seconds.. Nonetheless, the function pointer method isn't so terrific anyway, so this patch replaces it with a simple boolean, which also gets inlined away. This successfully works around the Clang bug. In general, I'm not too keen on all of the indirection involved here; it clearly does more harm than good. Hopefully the whole thing can get cleaned up down the road when lib/crypto is overhauled more comprehensively. But for now, we go with a simple bandaid. Fixes: 6048fdcc5f26 ("lib/crypto: blake2s: include as built-in") Reported-by: Miles Chen <miles.chen@mediatek.com> Tested-by: Miles Chen <miles.chen@mediatek.com> Tested-by: Nathan Chancellor <nathan@kernel.org> Link: https://github.com/ClangBuiltLinux/linux/issues/1567 Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Sami Tolvanen <samitolvanen@google.com> Cc: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> --- Changes v1->v2: - Wrapped columns at 80 for Eric. arch/arm/crypto/blake2s-shash.c | 4 ++-- arch/x86/crypto/blake2s-shash.c | 4 ++-- crypto/blake2s_generic.c | 4 ++-- include/crypto/internal/blake2s.h | 40 +++++++++++++++++++------------ lib/crypto/blake2s.c | 4 ++-- 5 files changed, 33 insertions(+), 23 deletions(-)