Date: Wed, 14 Aug 2019 09:56:59 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r351024 - in stable/12/sys: amd64/amd64 compat/freebsd32 compat/ia32 kern sys Message-ID: <201908140956.x7E9uxqD082476@repo.freebsd.org>
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Author: kib Date: Wed Aug 14 09:56:58 2019 New Revision: 351024 URL: https://svnweb.freebsd.org/changeset/base/351024 Log: MFC r350484, r350607, r350608: Make randomized stack gap between strings and pointers to argv/envs. Modified: stable/12/sys/amd64/amd64/elf_machdep.c stable/12/sys/compat/freebsd32/freebsd32_misc.c stable/12/sys/compat/ia32/ia32_sysvec.c stable/12/sys/kern/imgact_elf.c stable/12/sys/kern/kern_exec.c stable/12/sys/sys/imgact.h stable/12/sys/sys/imgact_elf.h stable/12/sys/sys/sysent.h Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/amd64/amd64/elf_machdep.c ============================================================================== --- stable/12/sys/amd64/amd64/elf_machdep.c Wed Aug 14 09:53:30 2019 (r351023) +++ stable/12/sys/amd64/amd64/elf_machdep.c Wed Aug 14 09:56:58 2019 (r351024) @@ -83,6 +83,7 @@ struct sysentvec elf64_freebsd_sysvec = { .sv_schedtail = NULL, .sv_thread_detach = NULL, .sv_trap = NULL, + .sv_stackgap = elf64_stackgap, }; INIT_SYSENTVEC(elf64_sysvec, &elf64_freebsd_sysvec); Modified: stable/12/sys/compat/freebsd32/freebsd32_misc.c ============================================================================== --- stable/12/sys/compat/freebsd32/freebsd32_misc.c Wed Aug 14 09:53:30 2019 (r351023) +++ stable/12/sys/compat/freebsd32/freebsd32_misc.c Wed Aug 14 09:56:58 2019 (r351024) @@ -3189,6 +3189,9 @@ freebsd32_copyout_strings(struct image_params *imgp) destp = rounddown2(destp, sizeof(uint32_t)); vectp = (uint32_t *)destp; + if (imgp->sysent->sv_stackgap != NULL) + imgp->sysent->sv_stackgap(imgp, (u_long *)&vectp); + if (imgp->auxargs) { /* * Allocate room on the stack for the ELF auxargs Modified: stable/12/sys/compat/ia32/ia32_sysvec.c ============================================================================== --- stable/12/sys/compat/ia32/ia32_sysvec.c Wed Aug 14 09:53:30 2019 (r351023) +++ stable/12/sys/compat/ia32/ia32_sysvec.c Wed Aug 14 09:56:58 2019 (r351024) @@ -129,6 +129,7 @@ struct sysentvec ia32_freebsd_sysvec = { .sv_schedtail = NULL, .sv_thread_detach = NULL, .sv_trap = NULL, + .sv_stackgap = elf32_stackgap, }; INIT_SYSENTVEC(elf_ia32_sysvec, &ia32_freebsd_sysvec); Modified: stable/12/sys/kern/imgact_elf.c ============================================================================== --- stable/12/sys/kern/imgact_elf.c Wed Aug 14 09:53:30 2019 (r351023) +++ stable/12/sys/kern/imgact_elf.c Wed Aug 14 09:56:58 2019 (r351024) @@ -157,6 +157,12 @@ SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, honor_sbrk, CTLFLA &__elfN(aslr_honor_sbrk), 0, __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) ": assume sbrk is used"); +static int __elfN(aslr_stack_gap) = 3; +SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, stack_gap, CTLFLAG_RW, + &__elfN(aslr_stack_gap), 0, + __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) + ": maximum percentage of main stack to waste on a random gap"); + static Elf_Brandinfo *elf_brand_list[MAX_BRANDS]; #define aligned(a, t) (rounddown2((u_long)(a), sizeof(t)) == (u_long)(a)) @@ -2723,4 +2729,24 @@ __elfN(untrans_prot)(vm_prot_t prot) if (prot & VM_PROT_WRITE) flags |= PF_W; return (flags); +} + +void +__elfN(stackgap)(struct image_params *imgp, u_long *stack_base) +{ + u_long range, rbase, gap; + int pct; + + if ((imgp->map_flags & MAP_ASLR) == 0) + return; + pct = __elfN(aslr_stack_gap); + if (pct == 0) + return; + if (pct > 50) + pct = 50; + range = imgp->eff_stack_sz * pct / 100; + arc4rand(&rbase, sizeof(rbase), 0); + gap = rbase % range; + gap &= ~(sizeof(u_long) - 1); + *stack_base -= gap; } Modified: stable/12/sys/kern/kern_exec.c ============================================================================== --- stable/12/sys/kern/kern_exec.c Wed Aug 14 09:53:30 2019 (r351023) +++ stable/12/sys/kern/kern_exec.c Wed Aug 14 09:56:58 2019 (r351024) @@ -1144,6 +1144,9 @@ exec_new_vmspace(struct image_params *imgp, struct sys } else { ssiz = maxssiz; } + imgp->eff_stack_sz = lim_cur(curthread, RLIMIT_STACK); + if (ssiz < imgp->eff_stack_sz) + imgp->eff_stack_sz = ssiz; stack_addr = sv->sv_usrstack - ssiz; error = vm_map_stack(map, stack_addr, (vm_size_t)ssiz, obj != NULL && imgp->stack_prot != 0 ? imgp->stack_prot : @@ -1538,6 +1541,9 @@ exec_copyout_strings(struct image_params *imgp) destp = rounddown2(destp, sizeof(void *)); vectp = (char **)destp; + if (imgp->sysent->sv_stackgap != NULL) + imgp->sysent->sv_stackgap(imgp, (u_long *)&vectp); + if (imgp->auxargs) { /* * Allocate room on the stack for the ELF auxargs Modified: stable/12/sys/sys/imgact.h ============================================================================== --- stable/12/sys/sys/imgact.h Wed Aug 14 09:53:30 2019 (r351023) +++ stable/12/sys/sys/imgact.h Wed Aug 14 09:56:58 2019 (r351024) @@ -86,6 +86,7 @@ struct image_params { int pagesizeslen; vm_prot_t stack_prot; u_long stack_sz; + u_long eff_stack_sz; struct ucred *newcred; /* new credentials if changing */ bool credential_setid; /* true if becoming setid */ bool textset; Modified: stable/12/sys/sys/imgact_elf.h ============================================================================== --- stable/12/sys/sys/imgact_elf.h Wed Aug 14 09:53:30 2019 (r351023) +++ stable/12/sys/sys/imgact_elf.h Wed Aug 14 09:56:58 2019 (r351024) @@ -98,6 +98,7 @@ int __elfN(remove_brand_entry)(Elf_Brandinfo *entry); int __elfN(freebsd_fixup)(register_t **, struct image_params *); int __elfN(coredump)(struct thread *, struct vnode *, off_t, int); size_t __elfN(populate_note)(int, void *, void *, size_t, void **); +void __elfN(stackgap)(struct image_params *, u_long *); /* Machine specific function to dump per-thread information. */ void __elfN(dump_thread)(struct thread *, void *, size_t *); Modified: stable/12/sys/sys/sysent.h ============================================================================== --- stable/12/sys/sys/sysent.h Wed Aug 14 09:53:30 2019 (r351023) +++ stable/12/sys/sys/sysent.h Wed Aug 14 09:56:58 2019 (r351024) @@ -110,6 +110,7 @@ struct sysentvec { int (*sv_coredump)(struct thread *, struct vnode *, off_t, int); /* function to dump core, or NULL */ int (*sv_imgact_try)(struct image_params *); + void (*sv_stackgap)(struct image_params *, u_long *); int sv_minsigstksz; /* minimum signal stack size */ int sv_pagesize; /* spare / no longer used */ vm_offset_t sv_minuser; /* VM_MIN_ADDRESS */
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