From: Mark Rutland <mark.rutland@arm.com> stable inclusion from stable-v6.6.123 commit ce820dd4e6e2d711242dc4331713b9bb4fe06d09 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/13576 CVE: CVE-2026-23102 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit b465ace42620970e840c7aeb2c44a6e3b1002fec ] Non-streaming SVE state may be preserved without an SVE payload, in which case the SVE context only has a header with VL==0, and all state can be restored from the FPSIMD context. Streaming SVE state is always preserved with an SVE payload, where the SVE context header has VL!=0, and the SVE_SIG_FLAG_SM flag is set. The kernel never preserves an SVE context where SVE_SIG_FLAG_SM is set without an SVE payload. However, restore_sve_fpsimd_context() doesn't forbid restoring such a context, and will handle this case by clearing PSTATE.SM and restoring the FPSIMD context into non-streaming mode, which isn't consistent with the SVE_SIG_FLAG_SM flag. Forbid this case, and mandate an SVE payload when the SVE_SIG_FLAG_SM flag is set. This avoids an awkward ABI quirk and reduces the risk that later rework to this code permits configuring a task with PSTATE.SM==1 and fp_type==FP_STATE_FPSIMD. I've marked this as a fix given that we never intended to support this case, and we don't want anyone to start relying upon the old behaviour once we re-enable SME. Fixes: 85ed24dad290 ("arm64/sme: Implement streaming SVE signal handling") Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Mark Brown <broonie@kernel.org> Cc: Will Deacon <will@kernel.org> Reviewed-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20250508132644.1395904-4-mark.rutland@arm.com Signed-off-by: Will Deacon <will@kernel.org> Stable-dep-of: d2907cbe9ea0 ("arm64/fpsimd: signal: Fix restoration of SVE context") Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Mingrui Liu <liumingrui@huawei.com> --- arch/arm64/kernel/signal.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index c378bc645e2a..38ee9bf6e162 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -219,6 +219,7 @@ int restore_sve_fpsimd_context(struct user_ctxs *user) unsigned int vl, vq; struct user_fpsimd_state fpsimd; u16 user_vl, flags; + bool sm; if (user->sve_size < sizeof(*user->sve)) return -EINVAL; @@ -228,7 +229,8 @@ int restore_sve_fpsimd_context(struct user_ctxs *user) if (err) return err; - if (flags & SVE_SIG_FLAG_SM) { + sm = flags & SVE_SIG_FLAG_SM; + if (sm) { if (!system_supports_sme()) return -EINVAL; @@ -248,7 +250,16 @@ int restore_sve_fpsimd_context(struct user_ctxs *user) if (user_vl != vl) return -EINVAL; - if (user->sve_size == sizeof(*user->sve)) { + /* + * Non-streaming SVE state may be preserved without an SVE payload, in + * which case the SVE context only has a header with VL==0, and all + * state can be restored from the FPSIMD context. + * + * Streaming SVE state is always preserved with an SVE payload. For + * consistency and robustness, reject restoring streaming SVE state + * without an SVE payload. + */ + if (!sm && user->sve_size == sizeof(*user->sve)) { clear_thread_flag(TIF_SVE); current->thread.svcr &= ~SVCR_SM_MASK; current->thread.fp_type = FP_STATE_FPSIMD; -- 2.34.1