On Monday, 21-Aug-2006 at 23:11 +0200, Willy Tarreau wrote:
> > > [...] But before this, I'd like to get comments from
> > > the people who discussed the subject recently.
> >
> > Thus, I think that both 2.4.33 and 2.6.<latest> are okay without any
> > further changes.
>
> At least 2.4 needs the fix to use the correct BAD_ADDR (which is not
> OK in 2.4.33 yet).
Ah, right. (Sorry, I was verifying the change in a RHEL3 tree.)
In that case, I support your patch as posted. But the whole point of
that investigation was to fix an exec() vulnerability with a bad ELF
entry address. This is addressed in the final hunk of the 2.4.33-based
patch below, which includes the changes that you previously posted.
Cheers. -ernie
Signed-off-by: Ernie Petrides <[email protected]>
--- linux-2.4.33/fs/binfmt_elf.c.orig
+++ linux-2.4.33/fs/binfmt_elf.c
@@ -77,7 +77,7 @@ static struct linux_binfmt elf_format =
NULL, THIS_MODULE, load_elf_binary, load_elf_library, elf_core_dump, ELF_EXEC_PAGESIZE
};
-#define BAD_ADDR(x) ((unsigned long)(x) > TASK_SIZE)
+#define BAD_ADDR(x) ((unsigned long)(x) >= TASK_SIZE)
static int set_brk(unsigned long start, unsigned long end)
{
@@ -345,7 +345,7 @@ elf_type, total_size);
* <= p_memsize so it is only necessary to check p_memsz.
*/
k = load_addr + eppnt->p_vaddr;
- if (k > TASK_SIZE || eppnt->p_filesz > eppnt->p_memsz ||
+ if (BAD_ADDR(k) || eppnt->p_filesz > eppnt->p_memsz ||
eppnt->p_memsz > TASK_SIZE || TASK_SIZE - eppnt->p_memsz < k) {
error = -ENOMEM;
goto out_close;
@@ -772,7 +772,7 @@ static int load_elf_binary(struct linux_
* allowed task size. Note that p_filesz must always be
* <= p_memsz so it is only necessary to check p_memsz.
*/
- if (k > TASK_SIZE || elf_ppnt->p_filesz > elf_ppnt->p_memsz ||
+ if (BAD_ADDR(k) || elf_ppnt->p_filesz > elf_ppnt->p_memsz ||
elf_ppnt->p_memsz > TASK_SIZE ||
TASK_SIZE - elf_ppnt->p_memsz < k) {
/* set_brk can never work. Avoid overflows. */
@@ -822,10 +822,9 @@ static int load_elf_binary(struct linux_
interpreter,
&interp_load_addr);
if (BAD_ADDR(elf_entry)) {
- printk(KERN_ERR "Unable to load interpreter %.128s\n",
- elf_interpreter);
force_sig(SIGSEGV, current);
- retval = IS_ERR((void *)elf_entry) ? PTR_ERR((void *)elf_entry) : -ENOEXEC;
+ retval = IS_ERR((void *)elf_entry) ?
+ (int)elf_entry : -EINVAL;
goto out_free_dentry;
}
reloc_func_desc = interp_load_addr;
@@ -833,6 +832,12 @@ static int load_elf_binary(struct linux_
allow_write_access(interpreter);
fput(interpreter);
kfree(elf_interpreter);
+ } else {
+ if (BAD_ADDR(elf_entry)) {
+ force_sig(SIGSEGV, current);
+ retval = -EINVAL;
+ goto out_free_dentry;
+ }
}
kfree(elf_phdata);
-
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