[PATCH 4/4] exec: copy-and-paste the fixes into compat_do_execve() paths - CVE-2010-NNN3

[Stefan Bader]

On 04.07.2011 17:35, Stefan Bader wrote:
> On 04.07.2011 12:03, paolo.pisati at canonical.com wrote:
>> From: Oleg Nesterov <oleg at redhat.com>
>>
>> BugLink: http://bugs.launchpad.net/bugs/804234
>>
>> commit 114279be2120a916e8a04feeb2ac976a10016f2f upstream.
>>
>> Note: this patch targets 2.6.37 and tries to be as simple as possible.
>> That is why it adds more copy-and-paste horror into fs/compat.c and
>> uglifies fs/exec.c, this will be cleanuped later.
>>
>> compat_copy_strings() plays with bprm->vma/mm directly and thus has
>> two problems: it lacks the RLIMIT_STACK check and argv/envp memory
>> is not visible to oom killer.
>>
>> Export acct_arg_size() and get_arg_page(), change compat_copy_strings()
>> to use get_arg_page(), change compat_do_execve() to do acct_arg_size(0)
>> as do_execve() does.
>>
>> Add the fatal_signal_pending/cond_resched checks into compat_count() and
>> compat_copy_strings(), this matches the code in fs/exec.c and certainly
>> makes sense.
>>
>> CVE-2010-NNN3
>>
>> Signed-off-by: Oleg Nesterov <oleg at redhat.com>
>> Cc: KOSAKI Motohiro <kosaki.motohiro at jp.fujitsu.com>
>> Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
>> Signed-off-by: Andi Kleen <ak at linux.intel.com>
>> Cc: Moritz Muehlenhoff <jmm at debian.org>
>> Signed-off-by: Greg Kroah-Hartman <gregkh at suse.de>
>> Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
>> Signed-off-by: Paolo Pisati <paolo.pisati at canonical.com>
>> ---
>>  fs/compat.c             |   28 +++++++++++++++-------------
>>  fs/exec.c               |    8 ++++----
>>  include/linux/binfmts.h |    4 ++++
>>  3 files changed, 23 insertions(+), 17 deletions(-)
>>
>> diff --git a/fs/compat.c b/fs/compat.c
>> index 6d6f98f..fc6eeae 100644
>> --- a/fs/compat.c
>> +++ b/fs/compat.c
>> @@ -1360,6 +1360,10 @@ static int compat_count(compat_uptr_t __user *argv, int max)
>>  			argv++;
>>  			if (i++ >= max)
>>  				return -E2BIG;
>> +
>> +			if (fatal_signal_pending(current))
>> +				return -ERESTARTNOHAND;
>> +			cond_resched();
>>  		}
>>  	}
>>  	return i;
>> @@ -1401,6 +1405,12 @@ static int compat_copy_strings(int argc, compat_uptr_t __user *argv,
>>  		while (len > 0) {
>>  			int offset, bytes_to_copy;
>>  
>> +			if (fatal_signal_pending(current)) {
>> +				ret = -ERESTARTNOHAND;
>> +				goto out;
>> +			}
>> +			cond_resched();
>> +
>>  			offset = pos % PAGE_SIZE;
>>  			if (offset == 0)
>>  				offset = PAGE_SIZE;
>> @@ -1417,18 +1427,8 @@ static int compat_copy_strings(int argc, compat_uptr_t __user *argv,
>>  			if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
>>  				struct page *page;
>>  
>> -#ifdef CONFIG_STACK_GROWSUP
>> -				ret = expand_stack_downwards(bprm->vma, pos);
>> -				if (ret < 0) {
>> -					/* We've exceed the stack rlimit. */
>> -					ret = -E2BIG;
>> -					goto out;
>> -				}
>> -#endif
>> -				ret = get_user_pages(current, bprm->mm, pos,
>> -						     1, 1, 1, &page, NULL);
>> -				if (ret <= 0) {
>> -					/* We've exceed the stack rlimit. */
>> +				page = get_arg_page(bprm, pos, 1);
>> +				if (!page) {
>>  					ret = -E2BIG;
>>  					goto out;
>>  				}
>> @@ -1549,8 +1549,10 @@ int compat_do_execve(char * filename,
>>  	return retval;
>>  
>>  out:
>> -	if (bprm->mm)
>> +	if (bprm->mm) {
>> +		acct_arg_size(bprm, 0);
>>  		mmput(bprm->mm);
>> +	}
>>  
>>  out_file:
>>  	if (bprm->file) {
>> diff --git a/fs/exec.c b/fs/exec.c
>> index 7b125a8..3bc6c91 100644
>> --- a/fs/exec.c
>> +++ b/fs/exec.c
>> @@ -159,7 +159,7 @@ out:
>>  
>>  #ifdef CONFIG_MMU
>>  
>> -static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
>> +void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
>>  {
>>  	struct mm_struct *mm = current->mm;
>>  	long diff = (long)(pages - bprm->vma_pages);
>> @@ -174,7 +174,7 @@ static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
>>  	up_write(&mm->mmap_sem);
>>  }
>>  
>> -static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
>> +struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
>>  		int write)
>>  {
>>  	struct page *page;
>> @@ -291,11 +291,11 @@ static bool valid_arg_len(struct linux_binprm *bprm, long len)
>>  
>>  #else
>>  
>> -static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
>> +void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
>>  {
>>  }
>>  
>> -static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
>> +struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
>>  		int write)
>>  {
>>  	struct page *page;
>> diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
>> index 48564ac..7f6c8e8 100644
>> --- a/include/linux/binfmts.h
>> +++ b/include/linux/binfmts.h
>> @@ -60,6 +60,10 @@ struct linux_binprm{
>>  	unsigned long loader, exec;
>>  };
>>  
>> +extern void acct_arg_size(struct linux_binprm *bprm, unsigned long pages);
>> +extern struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
>> +					int write);
>> +
>>  #define BINPRM_FLAGS_ENFORCE_NONDUMP_BIT 0
>>  #define BINPRM_FLAGS_ENFORCE_NONDUMP (1 << BINPRM_FLAGS_ENFORCE_NONDUMP_BIT)
>>  
> 
> I don't find CVE-2010-NNN3 somehow. But NNN3 is usually only temporary and then
> replaced by a real number...
> 
Think I found it: the full number for that seems to be CVE-2010-4243. If that
looks ok to you, I would replace the CVE number in the patch.

-Stefan