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rtld: Support multiple PT_GNU_RELRO program headers

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Iterate over all the program headers in obj_remap_relro and remove the
relro fields from Obj_Entry.

Skip the call to obj_enforce_relro() in relocate_object() for the rtld
object as well as the main program object.  obj_enforce_relro() is
called later when it safe to reference globals such as page_size.

Reviewed by:	kib
Obtained from:	CheriBSD
Sponsored by:	AFRL, DARPA
Differential Revision:	https://reviews.freebsd.org/D47884
This commit is contained in:
John Baldwin 2024-12-06 17:37:50 -05:00
parent 34f5de82e8
commit fda0403eb0
3 changed files with 20 additions and 32 deletions
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12
libexec/rtld-elf/map_object.c
View file

@ -93,8 +93,6 @@ map_object(int fd, const char *path, const struct stat *sb)
Elf_Addr bss_vlimit;
caddr_t bss_addr;
Elf_Word stack_flags;
Elf_Addr relro_page;
size_t relro_size;
Elf_Addr note_start;
Elf_Addr note_end;
char *note_map;
@ -114,8 +112,6 @@ map_object(int fd, const char *path, const struct stat *sb)
nsegs = -1;
phdyn = phinterp = phtls = NULL;
phdr_vaddr = 0;
relro_page = 0;
relro_size = 0;
note_start = 0;
note_end = 0;
note_map = NULL;
@ -161,11 +157,6 @@ map_object(int fd, const char *path, const struct stat *sb)
stack_flags = phdr->p_flags;
break;
case PT_GNU_RELRO:
relro_page = phdr->p_vaddr;
relro_size = phdr->p_memsz;
break;
case PT_NOTE:
if (phdr->p_offset > page_size ||
phdr->p_offset + phdr->p_filesz > page_size) {
@ -323,9 +314,6 @@ map_object(int fd, const char *path, const struct stat *sb)
obj->tlsinit = mapbase + phtls->p_vaddr;
}
obj->stack_flags = stack_flags;
obj->relro_page = obj->relocbase + rtld_trunc_page(relro_page);
obj->relro_size = rtld_trunc_page(relro_page + relro_size) -
rtld_trunc_page(relro_page);
if (note_start < note_end)
digest_notes(obj, note_start, note_end);
if (note_map != NULL)

37
libexec/rtld-elf/rtld.c
View file

@ -1672,12 +1672,6 @@ digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path)
obj->stack_flags = ph->p_flags;
break;
case PT_GNU_RELRO:
obj->relro_page = obj->relocbase + rtld_trunc_page(ph->p_vaddr);
obj->relro_size = rtld_trunc_page(ph->p_vaddr + ph->p_memsz) -
rtld_trunc_page(ph->p_vaddr);
break;
case PT_NOTE:
note_start = (Elf_Addr)obj->relocbase + ph->p_vaddr;
note_end = note_start + ph->p_filesz;
@ -2369,11 +2363,6 @@ parse_rtld_phdr(Obj_Entry *obj)
case PT_GNU_STACK:
obj->stack_flags = ph->p_flags;
break;
case PT_GNU_RELRO:
obj->relro_page = obj->relocbase +
rtld_trunc_page(ph->p_vaddr);
obj->relro_size = rtld_round_page(ph->p_memsz);
break;
case PT_NOTE:
note_start = (Elf_Addr)obj->relocbase + ph->p_vaddr;
note_end = note_start + ph->p_filesz;
@ -3328,7 +3317,7 @@ relocate_object(Obj_Entry *obj, bool bind_now, Obj_Entry *rtldobj,
lockstate) == -1)
return (-1);
if (!obj->mainprog && obj_enforce_relro(obj) == -1)
if (obj != rtldobj && !obj->mainprog && obj_enforce_relro(obj) == -1)
return (-1);
/*
@ -5909,12 +5898,26 @@ _rtld_is_dlopened(void *arg)
static int
obj_remap_relro(Obj_Entry *obj, int prot)
{
const Elf_Phdr *ph;
caddr_t relro_page;
size_t relro_size;
if (obj->relro_size > 0 && mprotect(obj->relro_page, obj->relro_size,
prot) == -1) {
_rtld_error("%s: Cannot set relro protection to %#x: %s",
obj->path, prot, rtld_strerror(errno));
return (-1);
for (ph = obj->phdr; (const char *)ph < (const char *)obj->phdr +
obj->phsize; ph++) {
switch (ph->p_type) {
case PT_GNU_RELRO:
relro_page = obj->relocbase +
rtld_trunc_page(ph->p_vaddr);
relro_size =
rtld_round_page(ph->p_vaddr + ph->p_memsz) -
rtld_trunc_page(ph->p_vaddr);
if (mprotect(relro_page, relro_size, prot) == -1) {
_rtld_error("%s: Cannot set relro protection to %#x: %s",
obj->path, prot, rtld_strerror(errno));
return (-1);
}
break;
}
}
return (0);
}

3
libexec/rtld-elf/rtld.h
View file

@ -165,9 +165,6 @@ typedef struct Struct_Obj_Entry {
size_t tlsalign; /* Alignment of static TLS block */
size_t tlspoffset; /* p_offset of the static TLS block */
caddr_t relro_page;
size_t relro_size;
/* Items from the dynamic section. */
Elf_Addr *pltgot; /* PLT or GOT, depending on architecture */
const Elf_Rel *rel; /* Relocation entries */