| Message ID | 20250326110059.3773318-1-keirf@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: mops: Do not dereference src reg for a set operation | expand |
On Wed, Mar 26, 2025 at 11:00:58AM +0000, Keir Fraser wrote: > The source register is not used for SET* and reading it can result in > a UBSAN out-of-bounds array access error, specifically when the MOPS > exception is taken from a SET* sequence with XZR (reg 31) as the > source. Architecturally this is the only case where a src/dst/size > field in the ESR can be reported as 31. > > Prior to 2de451a329cf662b the code in do_el0_mops() was benign as the > use of pt_regs_read_reg() prevented the out-of-bounds access. > > Fixes: 2de451a329cf662b ("KVM: arm64: Add handler for MOPS exceptions") > Cc: Kristina Martsenko <kristina.martsenko@arm.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: stable@vger.kernel.org > Reviewed-by: Marc Zyngier <maz@kernel.org> > Signed-off-by: Keir Fraser <keirf@google.com> Thanks! Acked-by: Mark Rutland <mark.rutland@arm.com> Mark. > --- > arch/arm64/include/asm/traps.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/traps.h b/arch/arm64/include/asm/traps.h > index d780d1bd2eac..82cf1f879c61 100644 > --- a/arch/arm64/include/asm/traps.h > +++ b/arch/arm64/include/asm/traps.h > @@ -109,10 +109,9 @@ static inline void arm64_mops_reset_regs(struct user_pt_regs *regs, unsigned lon > int dstreg = ESR_ELx_MOPS_ISS_DESTREG(esr); > int srcreg = ESR_ELx_MOPS_ISS_SRCREG(esr); > int sizereg = ESR_ELx_MOPS_ISS_SIZEREG(esr); > - unsigned long dst, src, size; > + unsigned long dst, size; > > dst = regs->regs[dstreg]; > - src = regs->regs[srcreg]; > size = regs->regs[sizereg]; > > /* > @@ -129,6 +128,7 @@ static inline void arm64_mops_reset_regs(struct user_pt_regs *regs, unsigned lon > } > } else { > /* CPY* instruction */ > + unsigned long src = regs->regs[srcreg]; > if (!(option_a ^ wrong_option)) { > /* Format is from Option B */ > if (regs->pstate & PSR_N_BIT) { > -- > 2.49.0.395.g12beb8f557-goog >
diff --git a/arch/arm64/include/asm/traps.h b/arch/arm64/include/asm/traps.h index d780d1bd2eac..82cf1f879c61 100644 --- a/arch/arm64/include/asm/traps.h +++ b/arch/arm64/include/asm/traps.h @@ -109,10 +109,9 @@ static inline void arm64_mops_reset_regs(struct user_pt_regs *regs, unsigned lon int dstreg = ESR_ELx_MOPS_ISS_DESTREG(esr); int srcreg = ESR_ELx_MOPS_ISS_SRCREG(esr); int sizereg = ESR_ELx_MOPS_ISS_SIZEREG(esr); - unsigned long dst, src, size; + unsigned long dst, size; dst = regs->regs[dstreg]; - src = regs->regs[srcreg]; size = regs->regs[sizereg]; /* @@ -129,6 +128,7 @@ static inline void arm64_mops_reset_regs(struct user_pt_regs *regs, unsigned lon } } else { /* CPY* instruction */ + unsigned long src = regs->regs[srcreg]; if (!(option_a ^ wrong_option)) { /* Format is from Option B */ if (regs->pstate & PSR_N_BIT) {
The source register is not used for SET* and reading it can result in a UBSAN out-of-bounds array access error, specifically when the MOPS exception is taken from a SET* sequence with XZR (reg 31) as the source. Architecturally this is the only case where a src/dst/size field in the ESR can be reported as 31. Prior to 2de451a329cf662b the code in do_el0_mops() was benign as the use of pt_regs_read_reg() prevented the out-of-bounds access. Fixes: 2de451a329cf662b ("KVM: arm64: Add handler for MOPS exceptions") Cc: Kristina Martsenko <kristina.martsenko@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will@kernel.org> Cc: stable@vger.kernel.org Reviewed-by: Marc Zyngier <maz@kernel.org> Signed-off-by: Keir Fraser <keirf@google.com> --- arch/arm64/include/asm/traps.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)