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capabilities: simplify bound checks for copy_from_user()

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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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
Arjan van de Ven 2009-10-14 08:17:36 +11:00 committed by James Morris
parent a27ab9f26b
commit 825332e4ff
1 changed files with 6 additions and 3 deletions
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9
kernel/capability.c
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@ -238,7 +238,7 @@ 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 +255,11 @@ 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++) {