From 4a242df81a9f9e347526afc36399a6880a59d6d2 Mon Sep 17 00:00:00 2001 From: kib Date: Fri, 18 Dec 2020 23:14:39 +0000 Subject: [PATCH] Add ELF flag to disable ASLR stack gap. Also centralize and unify checks to enable ASLR stack gap in a new helper exec_stackgap(). PR: 239873 Sponsored by: The FreeBSD Foundation MFC after: 1 week --- sys/compat/freebsd32/freebsd32_misc.c | 3 +-- sys/kern/imgact_elf.c | 2 -- sys/kern/kern_exec.c | 14 ++++++++++++-- sys/sys/elf_common.h | 1 + sys/sys/imgact.h | 1 + usr.bin/elfctl/elfctl.c | 1 + 6 files changed, 16 insertions(+), 6 deletions(-) diff --git a/sys/compat/freebsd32/freebsd32_misc.c b/sys/compat/freebsd32/freebsd32_misc.c index 6b7fd2deae3..62fab95c68d 100644 --- a/sys/compat/freebsd32/freebsd32_misc.c +++ b/sys/compat/freebsd32/freebsd32_misc.c @@ -3424,8 +3424,7 @@ freebsd32_copyout_strings(struct image_params *imgp, uintptr_t *stack_base) destp = rounddown2(destp, sizeof(uint32_t)); ustringp = destp; - if (imgp->sysent->sv_stackgap != NULL) - imgp->sysent->sv_stackgap(imgp, &destp); + exec_stackgap(imgp, &destp); if (imgp->auxargs) { /* diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c index fc1b7bf1a53..f6482bfcfb2 100644 --- a/sys/kern/imgact_elf.c +++ b/sys/kern/imgact_elf.c @@ -2818,8 +2818,6 @@ __elfN(stackgap)(struct image_params *imgp, uintptr_t *stack_base) uintptr_t range, rbase, gap; int pct; - if ((imgp->map_flags & MAP_ASLR) == 0) - return; pct = __elfN(aslr_stack_gap); if (pct == 0) return; diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c index b3fcbef0289..6f7c0147080 100644 --- a/sys/kern/kern_exec.c +++ b/sys/kern/kern_exec.c @@ -1534,6 +1534,17 @@ exec_args_get_begin_envv(struct image_args *args) return (args->endp); } +void +exec_stackgap(struct image_params *imgp, uintptr_t *dp) +{ + if (imgp->sysent->sv_stackgap == NULL || + (imgp->proc->p_fctl0 & (NT_FREEBSD_FCTL_ASLR_DISABLE | + NT_FREEBSD_FCTL_ASG_DISABLE)) != 0 || + (imgp->map_flags & MAP_ASLR) == 0) + return; + imgp->sysent->sv_stackgap(imgp, dp); +} + /* * Copy strings out to the new process address space, constructing new arg * and env vector tables. Return a pointer to the base so that it can be used @@ -1624,8 +1635,7 @@ exec_copyout_strings(struct image_params *imgp, uintptr_t *stack_base) destp = rounddown2(destp, sizeof(void *)); ustringp = destp; - if (imgp->sysent->sv_stackgap != NULL) - imgp->sysent->sv_stackgap(imgp, &destp); + exec_stackgap(imgp, &destp); if (imgp->auxargs) { /* diff --git a/sys/sys/elf_common.h b/sys/sys/elf_common.h index 8166d352955..5724397754e 100644 --- a/sys/sys/elf_common.h +++ b/sys/sys/elf_common.h @@ -797,6 +797,7 @@ typedef struct { #define NT_FREEBSD_FCTL_STKGAP_DISABLE 0x00000004 #define NT_FREEBSD_FCTL_WXNEEDED 0x00000008 #define NT_FREEBSD_FCTL_LA48 0x00000010 +#define NT_FREEBSD_FCTL_ASG_DISABLE 0x00000020 /* ASLR STACK GAP Disable */ /* Values for n_type. Used in core files. */ #define NT_PRSTATUS 1 /* Process status. */ diff --git a/sys/sys/imgact.h b/sys/sys/imgact.h index 5463b6f80d1..cd130551c05 100644 --- a/sys/sys/imgact.h +++ b/sys/sys/imgact.h @@ -122,6 +122,7 @@ int exec_copyin_args(struct image_args *, const char *, enum uio_seg, char **, char **); int exec_copyin_data_fds(struct thread *, struct image_args *, const void *, size_t, const int *, size_t); +void exec_stackgap(struct image_params *imgp, uintptr_t *dp); int pre_execve(struct thread *td, struct vmspace **oldvmspace); void post_execve(struct thread *td, int error, struct vmspace *oldvmspace); #endif diff --git a/usr.bin/elfctl/elfctl.c b/usr.bin/elfctl/elfctl.c index 591258fad72..e9b93e697ef 100644 --- a/usr.bin/elfctl/elfctl.c +++ b/usr.bin/elfctl/elfctl.c @@ -68,6 +68,7 @@ static struct ControlFeatures featurelist[] = { { "stackgap", NT_FREEBSD_FCTL_STKGAP_DISABLE, "Disable stack gap" }, { "wxneeded", NT_FREEBSD_FCTL_WXNEEDED, "Requires W+X mappings" }, { "la48", NT_FREEBSD_FCTL_LA48, "amd64: Limit user VA to 48bit" }, + { "aslrstkgap", NT_FREEBSD_FCTL_ASG_DISABLE, "Disable ASLR stack gap" }, }; static struct option long_opts[] = { -- 2.42.0