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setrlimit: Take stack gap into account.

Browse source 
Calling setrlimit with stack gap enabled and with low values of stack
resource limit often caused the program to abort immediately after
exiting the syscall. This happened due to the fact that the resource
limit was calculated assuming that the stack started at sv_usrstack,
while with stack gap enabled the stack is moved by a random number
of bytes.

Save information about stack size in struct vmspace and adjust the
rlim_cur value. If the rlim_cur and stack gap is bigger than rlim_max,
then the value is truncated to rlim_max.

PR: 253208
Reviewed by: kib
Obtained from: Semihalf
Sponsored by: Stormshield
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D31516
This commit is contained in:
Dawid Gorecki 2021-10-13 21:01:08 +02:00 committed by Marcin Wojtas
parent 1b0e2f0b60
commit 889b56c8cd
7 changed files with 19 additions and 7 deletions
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5
sys/kern/imgact_elf.c
View file

@ -2684,7 +2684,7 @@ __elfN(untrans_prot)(vm_prot_t prot)
return (flags);
}
void
vm_size_t
__elfN(stackgap)(struct image_params *imgp, uintptr_t *stack_base)
{
uintptr_t range, rbase, gap;
@ -2692,7 +2692,7 @@ __elfN(stackgap)(struct image_params *imgp, uintptr_t *stack_base)
pct = __elfN(aslr_stack_gap);
if (pct == 0)
return;
return (0);
if (pct > 50)
pct = 50;
range = imgp->eff_stack_sz * pct / 100;
@ -2700,4 +2700,5 @@ __elfN(stackgap)(struct image_params *imgp, uintptr_t *stack_base)
gap = rbase % range;
gap &= ~(sizeof(u_long) - 1);
*stack_base -= gap;
return (gap);
}

11
sys/kern/kern_exec.c
View file

@ -1148,6 +1148,7 @@ exec_new_vmspace(struct image_params *imgp, struct sysentvec *sv)
stack_prot, error, vm_mmap_to_errno(error));
return (vm_mmap_to_errno(error));
}
vmspace->vm_stkgap = 0;
/*
* vm_ssize and vm_maxsaddr are somewhat antiquated concepts, but they
@ -1493,12 +1494,16 @@ exec_args_get_begin_envv(struct image_args *args)
void
exec_stackgap(struct image_params *imgp, uintptr_t *dp)
{
struct proc *p = imgp->proc;
if (imgp->sysent->sv_stackgap == NULL ||
(imgp->proc->p_fctl0 & (NT_FREEBSD_FCTL_ASLR_DISABLE |
(p->p_fctl0 & (NT_FREEBSD_FCTL_ASLR_DISABLE |
NT_FREEBSD_FCTL_ASG_DISABLE)) != 0 ||
(imgp->map_flags & MAP_ASLR) == 0)
(imgp->map_flags & MAP_ASLR) == 0) {
p->p_vmspace->vm_stkgap = 0;
return;
imgp->sysent->sv_stackgap(imgp, dp);
}
p->p_vmspace->vm_stkgap = imgp->sysent->sv_stackgap(imgp, dp);
}
/*

3
sys/kern/kern_resource.c
View file

@ -671,6 +671,9 @@ kern_proc_setrlimit(struct thread *td, struct proc *p, u_int which,
if (limp->rlim_max < 0)
limp->rlim_max = RLIM_INFINITY;
if (which == RLIMIT_STACK && limp->rlim_cur != RLIM_INFINITY)
limp->rlim_cur += p->p_vmspace->vm_stkgap;
oldssiz.rlim_cur = 0;
newlim = lim_alloc();
PROC_LOCK(p);

2
sys/sys/imgact_elf.h
View file

@ -118,7 +118,7 @@ int __elfN(remove_brand_entry)(Elf_Brandinfo *entry);
int __elfN(freebsd_fixup)(uintptr_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 *, uintptr_t *);
vm_size_t __elfN(stackgap)(struct image_params *, uintptr_t *);
int __elfN(freebsd_copyout_auxargs)(struct image_params *, uintptr_t);
void __elfN(puthdr)(struct thread *, void *, size_t, int, size_t, int);
void __elfN(prepare_notes)(struct thread *, struct note_info_list *,

2
sys/sys/sysent.h
View file

@ -119,7 +119,7 @@ struct sysentvec {
void (*sv_elf_core_prepare_notes)(struct thread *,
struct note_info_list *, size_t *);
int (*sv_imgact_try)(struct image_params *);
void (*sv_stackgap)(struct image_params *, uintptr_t *);
vm_size_t (*sv_stackgap)(struct image_params *, uintptr_t *);
int (*sv_copyout_auxargs)(struct image_params *,
uintptr_t);
int sv_minsigstksz; /* minimum signal stack size */

2
sys/vm/vm_map.c
View file

@ -343,6 +343,7 @@ vmspace_alloc(vm_offset_t min, vm_offset_t max, pmap_pinit_t pinit)
vm->vm_taddr = 0;
vm->vm_daddr = 0;
vm->vm_maxsaddr = 0;
vm->vm_stkgap = 0;
return (vm);
}
@ -4265,6 +4266,7 @@ vmspace_fork(struct vmspace *vm1, vm_ooffset_t *fork_charge)
vm2->vm_taddr = vm1->vm_taddr;
vm2->vm_daddr = vm1->vm_daddr;
vm2->vm_maxsaddr = vm1->vm_maxsaddr;
vm2->vm_stkgap = vm1->vm_stkgap;
vm_map_lock(old_map);
if (old_map->busy)
vm_map_wait_busy(old_map);

1
sys/vm/vm_map.h
View file

@ -293,6 +293,7 @@ struct vmspace {
caddr_t vm_taddr; /* (c) user virtual address of text */
caddr_t vm_daddr; /* (c) user virtual address of data */
caddr_t vm_maxsaddr; /* user VA at max stack growth */
vm_size_t vm_stkgap; /* stack gap size in bytes */
u_int vm_refcnt; /* number of references */
/*
* Keep the PMAP last, so that CPU-specific variations of that