From 10b19249192ae28ee9092ceca327a83d27d88bd0 Mon Sep 17 00:00:00 2001 From: Alexey Dobriyan Date: Sun, 3 Oct 2021 15:11:24 +0300 Subject: ELF: fix overflow in total mapping size calculation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Kernel assumes that ELF program headers are ordered by mapping address, but doesn't enforce it. It is possible to make mapping size extremely huge by simply shuffling first and last PT_LOAD segments. As long as PT_LOAD segments do not overlap, it is silly to require sorting by v_addr anyway because mmap() doesn't care. Don't assume PT_LOAD segments are sorted and calculate min and max addresses correctly. Signed-off-by: Alexey Dobriyan Tested-by: "Magnus Groß" Link: https://lore.kernel.org/all/Yfqm7HbucDjPbES+@fractal.localdomain/ Signed-off-by: Kees Cook Link: https://lore.kernel.org/lkml/YVmd7D0M6G%2FDcP4O@localhost.localdomain --- fs/binfmt_elf.c | 23 +++++++++++------------ 1 file changed, 11 insertions(+), 12 deletions(-) (limited to 'fs/binfmt_elf.c') diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index c36b1ec357fb..65ea5381c5c7 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -93,7 +93,7 @@ static int elf_core_dump(struct coredump_params *cprm); #define ELF_CORE_EFLAGS 0 #endif -#define ELF_PAGESTART(_v) ((_v) & ~(unsigned long)(ELF_MIN_ALIGN-1)) +#define ELF_PAGESTART(_v) ((_v) & ~(int)(ELF_MIN_ALIGN-1)) #define ELF_PAGEOFFSET(_v) ((_v) & (ELF_MIN_ALIGN-1)) #define ELF_PAGEALIGN(_v) (((_v) + ELF_MIN_ALIGN - 1) & ~(ELF_MIN_ALIGN - 1)) @@ -399,22 +399,21 @@ static unsigned long elf_map(struct file *filep, unsigned long addr, return(map_addr); } -static unsigned long total_mapping_size(const struct elf_phdr *cmds, int nr) +static unsigned long total_mapping_size(const struct elf_phdr *phdr, int nr) { - int i, first_idx = -1, last_idx = -1; + elf_addr_t min_addr = -1; + elf_addr_t max_addr = 0; + bool pt_load = false; + int i; for (i = 0; i < nr; i++) { - if (cmds[i].p_type == PT_LOAD) { - last_idx = i; - if (first_idx == -1) - first_idx = i; + if (phdr[i].p_type == PT_LOAD) { + min_addr = min(min_addr, ELF_PAGESTART(phdr[i].p_vaddr)); + max_addr = max(max_addr, phdr[i].p_vaddr + phdr[i].p_memsz); + pt_load = true; } } - if (first_idx == -1) - return 0; - - return cmds[last_idx].p_vaddr + cmds[last_idx].p_memsz - - ELF_PAGESTART(cmds[first_idx].p_vaddr); + return pt_load ? (max_addr - min_addr) : 0; } static int elf_read(struct file *file, void *buf, size_t len, loff_t pos) -- cgit