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Message-ID: <CAGG-pUQ9u8V+Tqvw-FaiO8oayVvq9O+hdhZkAOPrGjvKpDp6vw@mail.gmail.com>
Date: Fri, 20 Sep 2013 13:57:22 -0300
From: Geyslan Gregório Bem <geyslan@...il.com>
To: viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
Joe Perches <joe@...ches.com>
Cc: linux-kernel@...r.kernel.org, "Geyslan G. Bem" <geyslan@...il.com>
Subject: Re: [PATCH v3 1/2] binfmt_aout: x86: Useless inode var, printks
coding style fixes
Hi guys,
Just to know whether the approach of my patches is correct.
[PATCH v3 1/2] binfmt_aout: x86: Useless inode var, printks coding style fixes
[PATCH v3 2/2] ia32_aout: x86_64: Add safe check in a.out loaders,
printks, conding style fixes
If so I'll start to sanitize the fs/exec.c
Please, reply.
Regards,
Geyslan Gregório Bem
hackingbits.com
2013/9/20 Geyslan G. Bem <geyslan@...il.com>:
> file size used only once, so removed due its useless prior allocation.
> It's not necessary to verify f_op in the load_aout_library, since the
> prior kernel_read/vfs_read function already does.
> Made coding style fixes and printk replacements.
>
> Tested using qemu, a handcrafted a.out binary and an a.out linked with a
> cross-compiled ld.
>
> Signed-off-by: Geyslan G. Bem <geyslan@...il.com>
> ---
> fs/binfmt_aout.c | 98 +++++++++++++++++++++++++++-----------------------------
> 1 file changed, 48 insertions(+), 50 deletions(-)
>
> diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c
> index 89dec7f..c732b8e 100644
> --- a/fs/binfmt_aout.c
> +++ b/fs/binfmt_aout.c
> @@ -25,13 +25,14 @@
> #include <linux/init.h>
> #include <linux/coredump.h>
> #include <linux/slab.h>
> +#include <linux/ratelimit.h>
> +#include <linux/uaccess.h>
>
> -#include <asm/uaccess.h>
> #include <asm/cacheflush.h>
> #include <asm/a.out-core.h>
>
> static int load_aout_binary(struct linux_binprm *);
> -static int load_aout_library(struct file*);
> +static int load_aout_library(struct file *);
>
> #ifdef CONFIG_COREDUMP
> /*
> @@ -62,7 +63,7 @@ static int aout_core_dump(struct coredump_params *cprm)
> fs = get_fs();
> set_fs(KERNEL_DS);
> has_dumped = 1;
> - strncpy(dump.u_comm, current->comm, sizeof(dump.u_comm));
> + strncpy(dump.u_comm, current->comm, sizeof(dump.u_comm));
> dump.u_ar0 = offsetof(struct user, regs);
> dump.signal = cprm->siginfo->si_signo;
> aout_dump_thread(cprm->regs, &dump);
> @@ -78,9 +79,11 @@ static int aout_core_dump(struct coredump_params *cprm)
>
> /* make sure we actually have a data and stack area to dump */
> set_fs(USER_DS);
> - if (!access_ok(VERIFY_READ, START_DATA(dump), dump.u_dsize << PAGE_SHIFT))
> + if (!access_ok(VERIFY_READ, START_DATA(dump),
> + dump.u_dsize << PAGE_SHIFT))
> dump.u_dsize = 0;
> - if (!access_ok(VERIFY_READ, START_STACK(dump), dump.u_ssize << PAGE_SHIFT))
> + if (!access_ok(VERIFY_READ, START_STACK(dump),
> + dump.u_ssize << PAGE_SHIFT))
> dump.u_ssize = 0;
>
> set_fs(KERNEL_DS);
> @@ -142,7 +145,8 @@ static int set_brk(unsigned long start, unsigned long end)
> * memory and creates the pointer tables from them, and puts their
> * addresses on the "stack", returning the new stack pointer value.
> */
> -static unsigned long __user *create_aout_tables(char __user *p, struct linux_binprm * bprm)
> +static unsigned long __user *create_aout_tables(char __user *p,
> + struct linux_binprm *bprm)
> {
> char __user * __user *argv;
> char __user * __user *envp;
> @@ -150,7 +154,8 @@ static unsigned long __user *create_aout_tables(char __user *p, struct linux_bin
> int argc = bprm->argc;
> int envc = bprm->envc;
>
> - sp = (void __user *)((-(unsigned long)sizeof(char *)) & (unsigned long) p);
> + sp = (void __user *) ((-(unsigned long) sizeof(char *))
> + & (unsigned long) p);
> #ifdef __alpha__
> /* whee.. test-programs are so much fun. */
> put_user(0, --sp);
> @@ -169,28 +174,28 @@ static unsigned long __user *create_aout_tables(char __user *p, struct linux_bin
> sp -= argc+1;
> argv = (char __user * __user *) sp;
> #ifndef __alpha__
> - put_user((unsigned long) envp,--sp);
> - put_user((unsigned long) argv,--sp);
> + put_user((unsigned long) envp, --sp);
> + put_user((unsigned long) argv, --sp);
> #endif
> - put_user(argc,--sp);
> + put_user(argc, --sp);
> current->mm->arg_start = (unsigned long) p;
> - while (argc-->0) {
> + while (argc-- > 0) {
> char c;
> - put_user(p,argv++);
> + put_user(p, argv++);
> do {
> - get_user(c,p++);
> + get_user(c, p++);
> } while (c);
> }
> - put_user(NULL,argv);
> + put_user(NULL, argv);
> current->mm->arg_end = current->mm->env_start = (unsigned long) p;
> - while (envc-->0) {
> + while (envc-- > 0) {
> char c;
> - put_user(p,envp++);
> + put_user(p, envp++);
> do {
> - get_user(c,p++);
> + get_user(c, p++);
> } while (c);
> }
> - put_user(NULL,envp);
> + put_user(NULL, envp);
> current->mm->env_end = (unsigned long) p;
> return sp;
> }
> @@ -200,7 +205,7 @@ static unsigned long __user *create_aout_tables(char __user *p, struct linux_bin
> * libraries. There is no binary dependent code anywhere else.
> */
>
> -static int load_aout_binary(struct linux_binprm * bprm)
> +static int load_aout_binary(struct linux_binprm *bprm)
> {
> struct pt_regs *regs = current_pt_regs();
> struct exec ex;
> @@ -213,7 +218,8 @@ static int load_aout_binary(struct linux_binprm * bprm)
> if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
> N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
> N_TRSIZE(ex) || N_DRSIZE(ex) ||
> - i_size_read(file_inode(bprm->file)) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
> + i_size_read(file_inode(bprm->file)) <
> + ex.a_text + ex.a_data + N_SYMSIZE(ex) + N_TXTOFF(ex)) {
> return -ENOEXEC;
> }
>
> @@ -292,19 +298,12 @@ static int load_aout_binary(struct linux_binprm * bprm)
> }
> } else {
> if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
> - (N_MAGIC(ex) != NMAGIC) && printk_ratelimit())
> - {
> - printk(KERN_NOTICE "executable not page aligned\n");
> - }
> -
> - if ((fd_offset & ~PAGE_MASK) != 0 && printk_ratelimit())
> - {
> - printk(KERN_WARNING
> - "fd_offset is not page aligned. Please convert program: %s\n",
> - bprm->file->f_path.dentry->d_name.name);
> - }
> + (N_MAGIC(ex) != NMAGIC))
> + pr_notice_ratelimited("executable not page aligned\n");
>
> - if (!bprm->file->f_op->mmap||((fd_offset & ~PAGE_MASK) != 0)) {
> + if ((fd_offset & ~PAGE_MASK) != 0) {
> + pr_warn_ratelimited("fd_offset is not page aligned. Please convert program: %s\n",
> + bprm->file->f_path.dentry->d_name.name);
> vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
> read_code(bprm->file, N_TXTADDR(ex), fd_offset,
> ex.a_text + ex.a_data);
> @@ -312,9 +311,10 @@ static int load_aout_binary(struct linux_binprm * bprm)
> }
>
> error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
> - PROT_READ | PROT_EXEC,
> - MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
> - fd_offset);
> + PROT_READ | PROT_EXEC,
> + (MAP_FIXED | MAP_PRIVATE
> + | MAP_DENYWRITE | MAP_EXECUTABLE),
> + fd_offset);
>
> if (error != N_TXTADDR(ex)) {
> send_sig(SIGKILL, current, 0);
> @@ -323,8 +323,10 @@ static int load_aout_binary(struct linux_binprm * bprm)
>
> error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
> PROT_READ | PROT_WRITE | PROT_EXEC,
> - MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE,
> + (MAP_FIXED | MAP_PRIVATE
> + | MAP_DENYWRITE | MAP_EXECUTABLE),
> fd_offset + ex.a_text);
> +
> if (error != N_DATADDR(ex)) {
> send_sig(SIGKILL, current, 0);
> return error;
> @@ -340,7 +342,8 @@ beyond_if:
> }
>
> current->mm->start_stack =
> - (unsigned long) create_aout_tables((char __user *) bprm->p, bprm);
> + (unsigned long) create_aout_tables((char __user *) bprm->p,
> + bprm);
> #ifdef __alpha__
> regs->gp = ex.a_gpvalue;
> #endif
> @@ -350,14 +353,11 @@ beyond_if:
>
> static int load_aout_library(struct file *file)
> {
> - struct inode * inode;
> unsigned long bss, start_addr, len;
> unsigned long error;
> int retval;
> struct exec ex;
>
> - inode = file_inode(file);
> -
> retval = -ENOEXEC;
> error = kernel_read(file, 0, (char *) &ex, sizeof(ex));
> if (error != sizeof(ex))
> @@ -366,7 +366,8 @@ static int load_aout_library(struct file *file)
> /* We come in here for the regular a.out style of shared libraries */
> if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
> N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
> - i_size_read(inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
> + i_size_read(file_inode(file)) <
> + ex.a_text + ex.a_data + N_SYMSIZE(ex) + N_TXTOFF(ex)) {
> goto out;
> }
>
> @@ -374,7 +375,7 @@ static int load_aout_library(struct file *file)
> * Requires a mmap handler. This prevents people from using a.out
> * as part of an exploit attack against /proc-related vulnerabilities.
> */
> - if (!file->f_op || !file->f_op->mmap)
> + if (!file->f_op->mmap)
> goto out;
>
> if (N_FLAGS(ex))
> @@ -383,17 +384,14 @@ static int load_aout_library(struct file *file)
> /* For QMAGIC, the starting address is 0x20 into the page. We mask
> this off to get the starting address for the page */
>
> - start_addr = ex.a_entry & 0xfffff000;
> + start_addr = ex.a_entry & 0xfffff000;
>
> if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
> - if (printk_ratelimit())
> - {
> - printk(KERN_WARNING
> - "N_TXTOFF is not page aligned. Please convert library: %s\n",
> - file->f_path.dentry->d_name.name);
> - }
> + pr_warn_ratelimited("N_TXTOFF is not page aligned. Please convert library: %s\n",
> + file->f_path.dentry->d_name.name);
> +
> vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
> -
> +
> read_code(file, start_addr, N_TXTOFF(ex),
> ex.a_text + ex.a_data);
> retval = 0;
> --
> 1.8.4
>
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