| Message ID | 20220117134403.2995059-1-npiggin@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | powerpc/64s: Mask SRR0 before checking against the masked NIP | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/github-powerpc_ppctests | success | Successfully ran 8 jobs. |
| snowpatch_ozlabs/github-powerpc_selftests | success | Successfully ran 8 jobs. |
| snowpatch_ozlabs/github-powerpc_sparse | success | Successfully ran 4 jobs. |
| snowpatch_ozlabs/github-powerpc_clang | success | Successfully ran 7 jobs. |
| snowpatch_ozlabs/github-powerpc_kernel_qemu | success | Successfully ran 24 jobs. |
On Mon, 17 Jan 2022 23:44:03 +1000, Nicholas Piggin wrote: > Commit 314f6c23dd8d ("powerpc/64s: Mask NIP before checking against > SRR0") masked off the low 2 bits of the NIP value in the interrupt > stack frame in case they are non-zero and mis-compare against a SRR0 > register value of a CPU which always reads back 0 from the 2 low bits > which are reserved. > > This now causes the opposite problem that an implementation which does > implement those bits in SRR0 will mis-compare against the masked NIP > value in which they have been cleared. QEMU is one such implementation, > and this is allowed by the architecture. > > [...] Applied to powerpc/fixes. [1/1] powerpc/64s: Mask SRR0 before checking against the masked NIP https://git.kernel.org/powerpc/c/aee101d7b95a03078945681dd7f7ea5e4a1e7686 cheers
diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S index 92088f848266..7bab2d7de372 100644 --- a/arch/powerpc/kernel/interrupt_64.S +++ b/arch/powerpc/kernel/interrupt_64.S @@ -30,6 +30,7 @@ COMPAT_SYS_CALL_TABLE: .ifc \srr,srr mfspr r11,SPRN_SRR0 ld r12,_NIP(r1) + clrrdi r11,r11,2 clrrdi r12,r12,2 100: tdne r11,r12 EMIT_WARN_ENTRY 100b,__FILE__,__LINE__,(BUGFLAG_WARNING | BUGFLAG_ONCE) @@ -40,6 +41,7 @@ COMPAT_SYS_CALL_TABLE: .else mfspr r11,SPRN_HSRR0 ld r12,_NIP(r1) + clrrdi r11,r11,2 clrrdi r12,r12,2 100: tdne r11,r12 EMIT_WARN_ENTRY 100b,__FILE__,__LINE__,(BUGFLAG_WARNING | BUGFLAG_ONCE)
Commit 314f6c23dd8d ("powerpc/64s: Mask NIP before checking against SRR0") masked off the low 2 bits of the NIP value in the interrupt stack frame in case they are non-zero and mis-compare against a SRR0 register value of a CPU which always reads back 0 from the 2 low bits which are reserved. This now causes the opposite problem that an implementation which does implement those bits in SRR0 will mis-compare against the masked NIP value in which they have been cleared. QEMU is one such implementation, and this is allowed by the architecture. This can be triggered by sigfuz by setting low bits of PT_NIP in the signal context. Fix this for now by masking the SRR0 bits as well. Cleaner is probably to sanitise these values before putting them in registers or stack, but this is the quick and backportable fix. Fixes: 314f6c23dd8d ("powerpc/64s: Mask NIP before checking against SRR0") Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/kernel/interrupt_64.S | 2 ++ 1 file changed, 2 insertions(+)