lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-Id: <20230929032435.2391507-5-keescook@chromium.org> Date: Thu, 28 Sep 2023 20:24:33 -0700 From: Kees Cook <keescook@...omium.org> To: Eric Biederman <ebiederm@...ssion.com> Cc: Kees Cook <keescook@...omium.org>, Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, Sebastian Ott <sebott@...hat.com>, Thomas Weißschuh <linux@...ssschuh.net>, Pedro Falcato <pedro.falcato@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: [PATCH v4 5/6] binfmt_elf: Only report padzero() errors when PROT_WRITE Errors with padzero() should be caught unless we're expecting a pathological (non-writable) segment. Report -EFAULT only when PROT_WRITE is present. Additionally add some more documentation to padzero(), elf_map(), and elf_load(). Cc: Eric Biederman <ebiederm@...ssion.com> Cc: Alexander Viro <viro@...iv.linux.org.uk> Cc: Christian Brauner <brauner@...nel.org> Cc: linux-fsdevel@...r.kernel.org Cc: linux-mm@...ck.org Suggested-by: Eric Biederman <ebiederm@...ssion.com> Signed-off-by: Kees Cook <keescook@...omium.org> --- fs/binfmt_elf.c | 32 +++++++++++++++++++++++--------- 1 file changed, 23 insertions(+), 9 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index f8b4747f87ed..22027b0a5923 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -110,19 +110,19 @@ static struct linux_binfmt elf_format = { #define BAD_ADDR(x) (unlikely((unsigned long)(x) >= TASK_SIZE)) -/* We need to explicitly zero any fractional pages - after the data section (i.e. bss). This would - contain the junk from the file that should not - be in memory +/* + * We need to explicitly zero any trailing portion of the page that follows + * p_filesz when it ends before the page ends (e.g. bss), otherwise this + * memory will contain the junk from the file that should not be present. */ -static int padzero(unsigned long elf_bss) +static int padzero(unsigned long address) { unsigned long nbyte; - nbyte = ELF_PAGEOFFSET(elf_bss); + nbyte = ELF_PAGEOFFSET(address); if (nbyte) { nbyte = ELF_MIN_ALIGN - nbyte; - if (clear_user((void __user *) elf_bss, nbyte)) + if (clear_user((void __user *)address, nbyte)) return -EFAULT; } return 0; @@ -348,6 +348,11 @@ create_elf_tables(struct linux_binprm *bprm, const struct elfhdr *exec, return 0; } +/* + * Map "eppnt->p_filesz" bytes from "filep" offset "eppnt->p_offset" + * into memory at "addr". (Note that p_filesz is rounded up to the + * next page, so any extra bytes from the file must be wiped.) + */ static unsigned long elf_map(struct file *filep, unsigned long addr, const struct elf_phdr *eppnt, int prot, int type, unsigned long total_size) @@ -387,6 +392,11 @@ static unsigned long elf_map(struct file *filep, unsigned long addr, return(map_addr); } +/* + * Map "eppnt->p_filesz" bytes from "filep" offset "eppnt->p_offset" + * into memory at "addr". Memory from "p_filesz" through "p_memsz" + * rounded up to the next page is zeroed. + */ static unsigned long elf_load(struct file *filep, unsigned long addr, const struct elf_phdr *eppnt, int prot, int type, unsigned long total_size) @@ -404,8 +414,12 @@ static unsigned long elf_load(struct file *filep, unsigned long addr, zero_end = map_addr + ELF_PAGEOFFSET(eppnt->p_vaddr) + eppnt->p_memsz; - /* Zero the end of the last mapped page */ - padzero(zero_start); + /* + * Zero the end of the last mapped page but ignore + * any errors if the segment isn't writable. + */ + if (padzero(zero_start) && (prot & PROT_WRITE)) + return -EFAULT; } } else { map_addr = zero_start = ELF_PAGESTART(addr); -- 2.34.1
Powered by blists - more mailing lists