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Riedl" To: linuxppc-dev@lists.ozlabs.org Cc: tglx@linutronix.de, x86@kernel.org, linux-hardening@vger.kernel.org, keescook@chromium.org, npiggin@gmail.com, dja@axtens.net, peterz@infradead.org Subject: [PATCH v5 6/8] powerpc: Rework and improve STRICT_KERNEL_RWX patching Date: Tue, 13 Jul 2021 00:31:11 -0500 Message-Id: <20210713053113.4632-7-cmr@linux.ibm.com> X-Mailer: git-send-email 2.26.1 In-Reply-To: <20210713053113.4632-1-cmr@linux.ibm.com> References: <20210713053113.4632-1-cmr@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-GUID: ECjsolDe6qEUnWRzIsgM-nmy61gmL3Uw X-Proofpoint-ORIG-GUID: B9H47KRkzfDhVNM7R0btHcTPLGaYrbsW X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-07-13_03:2021-07-13,2021-07-12 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 malwarescore=0 suspectscore=0 impostorscore=0 phishscore=0 priorityscore=1501 spamscore=0 mlxlogscore=853 bulkscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107130022 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org Rework code-patching with STRICT_KERNEL_RWX to prepare for the next patch which uses a temporary mm for patching under the Book3s64 Radix MMU. Make improvements by adding a WARN_ON when the patchsite doesn't match after patching and return the error from __patch_instruction() properly. Signed-off-by: Christopher M. Riedl --- v5: * New to series. --- arch/powerpc/lib/code-patching.c | 51 +++++++++++++++++--------------- 1 file changed, 27 insertions(+), 24 deletions(-) diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-pat= ching.c index 3122d8e4cc013..9f2eba9b70ee4 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -102,11 +102,12 @@ static inline void unuse_temporary_mm(struct temp_m= m *temp_mm) } =20 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area); +static DEFINE_PER_CPU(unsigned long, cpu_patching_addr); =20 #if IS_BUILTIN(CONFIG_LKDTM) unsigned long read_cpu_patching_addr(unsigned int cpu) { - return (unsigned long)(per_cpu(text_poke_area, cpu))->addr; + return per_cpu(cpu_patching_addr, cpu); } #endif =20 @@ -121,6 +122,7 @@ static int text_area_cpu_up(unsigned int cpu) return -1; } this_cpu_write(text_poke_area, area); + this_cpu_write(cpu_patching_addr, (unsigned long)area->addr); =20 return 0; } @@ -146,7 +148,7 @@ void __init poking_init(void) /* * This can be called for kernel text or a module. */ -static int map_patch_area(void *addr, unsigned long text_poke_addr) +static int map_patch_area(void *addr) { unsigned long pfn; int err; @@ -156,17 +158,20 @@ static int map_patch_area(void *addr, unsigned long= text_poke_addr) else pfn =3D __pa_symbol(addr) >> PAGE_SHIFT; =20 - err =3D map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNE= L); + err =3D map_kernel_page(__this_cpu_read(cpu_patching_addr), + (pfn << PAGE_SHIFT), PAGE_KERNEL); =20 - pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err)= ; + pr_devel("Mapped addr %lx with pfn %lx:%d\n", + __this_cpu_read(cpu_patching_addr), pfn, err); if (err) return -1; =20 return 0; } =20 -static inline int unmap_patch_area(unsigned long addr) +static inline int unmap_patch_area(void) { + unsigned long addr =3D __this_cpu_read(cpu_patching_addr); pte_t *ptep; pmd_t *pmdp; pud_t *pudp; @@ -175,23 +180,23 @@ static inline int unmap_patch_area(unsigned long ad= dr) =20 pgdp =3D pgd_offset_k(addr); if (unlikely(!pgdp)) - return -EINVAL; + goto out_err; =20 p4dp =3D p4d_offset(pgdp, addr); if (unlikely(!p4dp)) - return -EINVAL; + goto out_err; =20 pudp =3D pud_offset(p4dp, addr); if (unlikely(!pudp)) - return -EINVAL; + goto out_err; =20 pmdp =3D pmd_offset(pudp, addr); if (unlikely(!pmdp)) - return -EINVAL; + goto out_err; =20 ptep =3D pte_offset_kernel(pmdp, addr); if (unlikely(!ptep)) - return -EINVAL; + goto out_err; =20 pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr); =20 @@ -202,15 +207,17 @@ static inline int unmap_patch_area(unsigned long ad= dr) flush_tlb_kernel_range(addr, addr + PAGE_SIZE); =20 return 0; + +out_err: + pr_warn("failed to unmap %lx\n", addr); + return -EINVAL; } =20 static int do_patch_instruction(u32 *addr, struct ppc_inst instr) { - int err; + int err, rc =3D 0; u32 *patch_addr =3D NULL; unsigned long flags; - unsigned long text_poke_addr; - unsigned long kaddr =3D (unsigned long)addr; =20 /* * During early early boot patch_instruction is called @@ -222,24 +229,20 @@ static int do_patch_instruction(u32 *addr, struct p= pc_inst instr) =20 local_irq_save(flags); =20 - text_poke_addr =3D (unsigned long)__this_cpu_read(text_poke_area)->addr= ; - if (map_patch_area(addr, text_poke_addr)) { - err =3D -1; + err =3D map_patch_area(addr); + if (err) goto out; - } - - patch_addr =3D (u32 *)(text_poke_addr + (kaddr & ~PAGE_MASK)); =20 - __patch_instruction(addr, instr, patch_addr); + patch_addr =3D (u32 *)(__this_cpu_read(cpu_patching_addr) | offset_in_p= age(addr)); + rc =3D __patch_instruction(addr, instr, patch_addr); =20 - err =3D unmap_patch_area(text_poke_addr); - if (err) - pr_warn("failed to unmap %lx\n", text_poke_addr); + err =3D unmap_patch_area(); =20 out: local_irq_restore(flags); + WARN_ON(!ppc_inst_equal(ppc_inst_read(addr), instr)); =20 - return err; + return rc ? rc : err; } #else /* !CONFIG_STRICT_KERNEL_RWX */ =20 --=20 2.26.1