Author: kib
Date: Fri Dec 18 23:14:39 2020
New Revision: 368772
URL: https://svnweb.freebsd.org/changeset/base/368772
Log:
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
Modified:
head/sys/compat/freebsd32/freebsd32_misc.c
head/sys/kern/imgact_elf.c
head/sys/kern/kern_exec.c
head/sys/sys/elf_common.h
head/sys/sys/imgact.h
head/usr.bin/elfctl/elfctl.c
Modified: head/sys/compat/freebsd32/freebsd32_misc.c
==============================================================================
--- head/sys/compat/freebsd32/freebsd32_misc.c Fri Dec 18 23:11:27 2020
(r368771)
+++ head/sys/compat/freebsd32/freebsd32_misc.c Fri Dec 18 23:14:39 2020
(r368772)
@@ -3424,8 +3424,7 @@ freebsd32_copyout_strings(struct image_params *imgp, u
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) {
/*
Modified: head/sys/kern/imgact_elf.c
==============================================================================
--- head/sys/kern/imgact_elf.c Fri Dec 18 23:11:27 2020 (r368771)
+++ head/sys/kern/imgact_elf.c Fri Dec 18 23:14:39 2020 (r368772)
@@ -2818,8 +2818,6 @@ __elfN(stackgap)(struct image_params *imgp, uintptr_t
uintptr_t range, rbase, gap;
int pct;
- if ((imgp->map_flags & MAP_ASLR) == 0)
- return;
pct = __elfN(aslr_stack_gap);
if (pct == 0)
return;
Modified: head/sys/kern/kern_exec.c
==============================================================================
--- head/sys/kern/kern_exec.c Fri Dec 18 23:11:27 2020 (r368771)
+++ head/sys/kern/kern_exec.c Fri Dec 18 23:14:39 2020 (r368772)
@@ -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, uintpt
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) {
/*
Modified: head/sys/sys/elf_common.h
==============================================================================
--- head/sys/sys/elf_common.h Fri Dec 18 23:11:27 2020 (r368771)
+++ head/sys/sys/elf_common.h Fri Dec 18 23:14:39 2020 (r368772)
@@ -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. */
Modified: head/sys/sys/imgact.h
==============================================================================
--- head/sys/sys/imgact.h Fri Dec 18 23:11:27 2020 (r368771)
+++ head/sys/sys/imgact.h Fri Dec 18 23:14:39 2020 (r368772)
@@ -122,6 +122,7 @@ int exec_copyin_args(struct image_args *, const char *
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
Modified: head/usr.bin/elfctl/elfctl.c
==============================================================================
--- head/usr.bin/elfctl/elfctl.c Fri Dec 18 23:11:27 2020
(r368771)
+++ head/usr.bin/elfctl/elfctl.c Fri Dec 18 23:14:39 2020
(r368772)
@@ -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[] = {
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