Messages in this thread Patch in this message | | | Date | Thu, 8 Oct 2009 06:42:21 -0700 | From | Arjan van de Ven <> | Subject | Re: linux-next: build warnings (buffer size is not provably correct) |
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On Thu, 8 Oct 2009 15:47:10 +1100 Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> Hi all, > > Today's linux-next build (i386 defconfig) produced these warnings: > > In file included from arch/x86/include/asm/uaccess.h:572, > from kernel/capability.c:18: > arch/x86/include/asm/uaccess_32.h: In function 'sys_capset':
the following needs to go somewhere... Andrew ?
From: Arjan van de Ven <arjan@linux.intel.com> Subject: [PATCH 7/9] Simplify bound checks in capabilities for copy_from_user CC: James Morris <jmorris@namei.org>
The capabilities syscall has a copy_from_user() call where gcc currently cannot prove to itself that the copy is always within bounds.
This patch adds a very explicity bound check to prove to gcc that this copy_from_user cannot overflow its destination buffer.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Acked-by: James Morris <jmorris@namei.org>
diff --git a/kernel/capability.c b/kernel/capability.c index 4e17041..204f11f 100644 --- a/kernel/capability.c +++ b/kernel/capability.c @@ -238,7 +241,7 @@ SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr) SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data) { struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S]; - unsigned i, tocopy; + unsigned i, tocopy, copybytes; kernel_cap_t inheritable, permitted, effective; struct cred *new; int ret; @@ -255,8 +258,11 @@ SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data) if (pid != 0 && pid != task_pid_vnr(current)) return -EPERM; - if (copy_from_user(&kdata, data, - tocopy * sizeof(struct __user_cap_data_struct))) + copybytes = tocopy * sizeof(struct __user_cap_data_struct); + if (copybytes > sizeof(kdata)) + return -EFAULT; + + if (copy_from_user(&kdata, data, copybytes)) return -EFAULT; for (i = 0; i < tocopy; i++) {
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