From 3c77f845722158206a7209c45ccddc264d19319c Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 30 Nov 2010 20:55:34 +0100 Subject: exec: make argv/envp memory visible to oom-killer Brad Spengler published a local memory-allocation DoS that evades the OOM-killer (though not the virtual memory RLIMIT): http://www.grsecurity.net/~spender/64bit_dos.c execve()->copy_strings() can allocate a lot of memory, but this is not visible to oom-killer, nobody can see the nascent bprm->mm and take it into account. With this patch get_arg_page() increments current's MM_ANONPAGES counter every time we allocate the new page for argv/envp. When do_execve() succeds or fails, we change this counter back. Technically this is not 100% correct, we can't know if the new page is swapped out and turn MM_ANONPAGES into MM_SWAPENTS, but I don't think this really matters and everything becomes correct once exec changes ->mm or fails. Reported-by: Brad Spengler Reviewed-and-discussed-by: KOSAKI Motohiro Signed-off-by: Oleg Nesterov Cc: stable@kernel.org Signed-off-by: Linus Torvalds --- include/linux/binfmts.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/binfmts.h') diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index a065612fc928..7c87796d20da 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -29,6 +29,7 @@ struct linux_binprm{ char buf[BINPRM_BUF_SIZE]; #ifdef CONFIG_MMU struct vm_area_struct *vma; + unsigned long vma_pages; #else # define MAX_ARG_PAGES 32 struct page *page[MAX_ARG_PAGES]; -- cgit v1.2.2 From 114279be2120a916e8a04feeb2ac976a10016f2f Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 30 Nov 2010 20:56:02 +0100 Subject: exec: copy-and-paste the fixes into compat_do_execve() paths 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. Signed-off-by: Oleg Nesterov Cc: KOSAKI Motohiro Cc: stable@kernel.org Signed-off-by: Linus Torvalds --- include/linux/binfmts.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux/binfmts.h') diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index 7c87796d20da..64a7114a9394 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) -- cgit v1.2.2