The branch main has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=714d6d09b57e9cf98a5c3f45f869c08be5454849
commit 714d6d09b57e9cf98a5c3f45f869c08be5454849 Author: Konstantin Belousov <[email protected]> AuthorDate: 2021-12-08 09:33:57 +0000 Commit: Konstantin Belousov <[email protected]> CommitDate: 2021-12-12 14:28:38 +0000 imgact_elf: exclude invalid alignment requests Only accept at most superpage alignment, or if the arch does not have superpages supported, artificially limit it to PAGE_SIZE * 1024. This is somewhat arbitrary, and e.g. could change what binaries do we accept between native i386 vs. amd64 ia32 with superpages disabled, but I do not believe the difference there is affecting anybody with real (useful) binaries. Reported and tested by: pho Reviewed by: markj Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D33359 --- sys/kern/imgact_elf.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c index 7e7d4bdc1647..3b05b38f3ed1 100644 --- a/sys/kern/imgact_elf.c +++ b/sys/kern/imgact_elf.c @@ -1112,7 +1112,7 @@ __CONCAT(exec_, __elfN(imgact))(struct image_params *imgp) Elf_Brandinfo *brand_info; struct sysentvec *sv; u_long addr, baddr, et_dyn_addr, entry, proghdr; - u_long maxalign, mapsz, maxv, maxv1; + u_long maxalign, maxsalign, mapsz, maxv, maxv1; uint32_t fctl0; int32_t osrel; bool free_interp; @@ -1153,7 +1153,20 @@ __CONCAT(exec_, __elfN(imgact))(struct image_params *imgp) interp = NULL; free_interp = false; td = curthread; + + /* + * Somewhat arbitrary, limit accepted max alignment for the + * loadable segment to the max supported superpage size. Too + * large alignment requests are not useful and are indicators + * of corrupted or outright malicious binary. + */ maxalign = PAGE_SIZE; + maxsalign = PAGE_SIZE * 1024; + for (i = MAXPAGESIZES - 1; i > 0; i--) { + if (pagesizes[i] > maxsalign) + maxsalign = pagesizes[i]; + } + mapsz = 0; for (i = 0; i < hdr->e_phnum; i++) { @@ -1161,6 +1174,11 @@ __CONCAT(exec_, __elfN(imgact))(struct image_params *imgp) case PT_LOAD: if (n == 0) baddr = phdr[i].p_vaddr; + if (phdr[i].p_align > maxsalign) { + uprintf("Invalid segment alignment\n"); + error = ENOEXEC; + goto ret; + } if (phdr[i].p_align > maxalign) maxalign = phdr[i].p_align; mapsz += phdr[i].p_memsz;
