Apply mapping protections to .o kernel modules.
Use the section flags to derive mapping protections. When multiple sections overlap within a page, the union of their protections must be applied. With r353701 the .text and .rodata sections are padded to ensure that this does not happen on amd64. Reviewed by: kib MFC after: 1 month Sponsored by: Netflix Differential Revision: https://reviews.freebsd.org/D21896
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parent
44a57bfe3a
commit
1d9eae9fb2
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=353729
@ -70,8 +70,8 @@ __FBSDID("$FreeBSD$");
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typedef struct {
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void *addr;
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Elf_Off size;
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int flags;
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int sec; /* Original section */
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int flags; /* Section flags. */
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int sec; /* Original section number. */
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char *name;
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} Elf_progent;
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@ -196,6 +196,119 @@ link_elf_init(void *arg)
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SYSINIT(link_elf_obj, SI_SUB_KLD, SI_ORDER_SECOND, link_elf_init, NULL);
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static void
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link_elf_protect_range(elf_file_t ef, vm_offset_t start, vm_offset_t end,
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vm_prot_t prot)
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{
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int error __unused;
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KASSERT(start <= end && start >= (vm_offset_t)ef->address &&
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end <= round_page((vm_offset_t)ef->address + ef->lf.size),
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("link_elf_protect_range: invalid range %#jx-%#jx",
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(uintmax_t)start, (uintmax_t)end));
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if (start == end)
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return;
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error = vm_map_protect(kernel_map, start, end, prot, FALSE);
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KASSERT(error == KERN_SUCCESS,
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("link_elf_protect_range: vm_map_protect() returned %d", error));
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}
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/*
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* Restrict permissions on linker file memory based on section flags.
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* Sections need not be page-aligned, so overlap within a page is possible.
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*/
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static void
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link_elf_protect(elf_file_t ef)
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{
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vm_offset_t end, segend, segstart, start;
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vm_prot_t gapprot, prot, segprot;
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int i;
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/*
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* If the file was preloaded, the last page may contain other preloaded
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* data which may need to be writeable. ELF files are always
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* page-aligned, but other preloaded data, such as entropy or CPU
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* microcode may be loaded with a smaller alignment.
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*/
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gapprot = ef->preloaded ? VM_PROT_RW : VM_PROT_READ;
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start = end = (vm_offset_t)ef->address;
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prot = VM_PROT_READ;
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for (i = 0; i < ef->nprogtab; i++) {
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/*
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* VNET and DPCPU sections have their memory allocated by their
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* respective subsystems.
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*/
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if (ef->progtab[i].name != NULL && (
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#ifdef VIMAGE
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strcmp(ef->progtab[i].name, VNET_SETNAME) == 0 ||
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#endif
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strcmp(ef->progtab[i].name, DPCPU_SETNAME) == 0))
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continue;
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segstart = trunc_page((vm_offset_t)ef->progtab[i].addr);
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segend = round_page((vm_offset_t)ef->progtab[i].addr +
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ef->progtab[i].size);
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segprot = VM_PROT_READ;
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if ((ef->progtab[i].flags & SHF_WRITE) != 0)
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segprot |= VM_PROT_WRITE;
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if ((ef->progtab[i].flags & SHF_EXECINSTR) != 0)
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segprot |= VM_PROT_EXECUTE;
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if (end <= segstart) {
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/*
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* Case 1: there is no overlap between the previous
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* segment and this one. Apply protections to the
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* previous segment, and protect the gap between the
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* previous and current segments, if any.
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*/
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link_elf_protect_range(ef, start, end, prot);
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link_elf_protect_range(ef, end, segstart, gapprot);
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start = segstart;
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end = segend;
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prot = segprot;
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} else if (start < segstart && end == segend) {
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/*
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* Case 2: the current segment is a subrange of the
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* previous segment. Apply protections to the
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* non-overlapping portion of the previous segment.
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*/
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link_elf_protect_range(ef, start, segstart, prot);
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start = segstart;
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prot |= segprot;
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} else if (end < segend) {
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/*
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* Case 3: there is partial overlap between the previous
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* and current segments. Apply protections to the
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* non-overlapping portion of the previous segment, and
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* then the overlap, which must use the union of the two
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* segments' protections.
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*/
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link_elf_protect_range(ef, start, segstart, prot);
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link_elf_protect_range(ef, segstart, end,
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prot | segprot);
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start = end;
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end = segend;
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prot = segprot;
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} else {
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/*
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* Case 4: the two segments reside in the same page.
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*/
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prot |= segprot;
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}
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}
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/*
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* Fix up the last unprotected segment and trailing data.
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*/
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link_elf_protect_range(ef, start, end, prot);
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link_elf_protect_range(ef, end,
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round_page((vm_offset_t)ef->address + ef->lf.size), gapprot);
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}
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static int
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link_elf_link_preload(linker_class_t cls, const char *filename,
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linker_file_t *result)
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@ -358,6 +471,7 @@ link_elf_link_preload(linker_class_t cls, const char *filename,
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else
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ef->progtab[pb].name = "<<NOBITS>>";
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ef->progtab[pb].size = shdr[i].sh_size;
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ef->progtab[pb].flags = shdr[i].sh_flags;
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ef->progtab[pb].sec = i;
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if (ef->shstrtab && shdr[i].sh_name != 0)
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ef->progtab[pb].name =
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@ -783,7 +897,9 @@ link_elf_load_file(linker_class_t cls, const char *filename,
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/*
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* In order to satisfy amd64's architectural requirements on the
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* location of code and data in the kernel's address space, request a
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* mapping that is above the kernel.
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* mapping that is above the kernel.
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*
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* Protections will be restricted once relocations are applied.
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*/
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#ifdef __amd64__
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mapbase = KERNBASE;
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@ -884,6 +1000,7 @@ link_elf_load_file(linker_class_t cls, const char *filename,
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goto out;
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}
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ef->progtab[pb].size = shdr[i].sh_size;
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ef->progtab[pb].flags = shdr[i].sh_flags;
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ef->progtab[pb].sec = i;
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if (shdr[i].sh_type == SHT_PROGBITS
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#ifdef __amd64__
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@ -1023,9 +1140,8 @@ link_elf_load_file(linker_class_t cls, const char *filename,
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goto out;
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#endif
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/* Invoke .ctors */
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link_elf_protect(ef);
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link_elf_invoke_ctors(lf->ctors_addr, lf->ctors_size);
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*result = lf;
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out:
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