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Subject[PATCH 09/33] x86/fpu: Change 'size_total' parameter to unsigned and standardize the size checks in copy_xstate_to_*()
Date
'size_total' is derived from an unsigned input parameter - and then converted
to 'int' and checked for negative ranges:

if (size_total < 0 || offset < size_total) {

This conversion and the checks are unnecessary obfuscation, reject overly
large requested copy sizes outright and simplify the underlying code.

Reported-by: Rik van Riel <riel@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/fpu/xstate.c | 32 +++++++++++++++-----------------
1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index c13083579655..b18c5457065a 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -925,15 +925,11 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
* the source data pointer or increment pos, count, kbuf, and ubuf.
*/
static inline int
-__copy_xstate_to_kernel(void *kbuf,
- const void *data,
- unsigned int offset, unsigned int size, int size_total)
+__copy_xstate_to_kernel(void *kbuf, const void *data,
+ unsigned int offset, unsigned int size, unsigned int size_total)
{
- if (!size)
- return 0;
-
- if (size_total < 0 || offset < size_total) {
- unsigned int copy = size_total < 0 ? size : min(size, size_total - offset);
+ if (offset < size_total) {
+ unsigned int copy = min(size, size_total - offset);

memcpy(kbuf + offset, data, copy);
}
@@ -986,12 +982,13 @@ int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int of
offset = xstate_offsets[i];
size = xstate_sizes[i];

+ /* The next component has to fit fully into the output buffer: */
+ if (offset + size > size_total)
+ break;
+
ret = __copy_xstate_to_kernel(kbuf, src, offset, size, size_total);
if (ret)
return ret;
-
- if (offset + size >= size_total)
- break;
}

}
@@ -1010,13 +1007,13 @@ int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int of
}

static inline int
-__copy_xstate_to_user(void __user *ubuf, const void *data, unsigned int offset, unsigned int size, int size_total)
+__copy_xstate_to_user(void __user *ubuf, const void *data, unsigned int offset, unsigned int size, unsigned int size_total)
{
if (!size)
return 0;

- if (size_total < 0 || offset < size_total) {
- unsigned int copy = size_total < 0 ? size : min(size, size_total - offset);
+ if (offset < size_total) {
+ unsigned int copy = min(size, size_total - offset);

if (__copy_to_user(ubuf + offset, data, copy))
return -EFAULT;
@@ -1069,12 +1066,13 @@ int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned i
offset = xstate_offsets[i];
size = xstate_sizes[i];

+ /* The next component has to fit fully into the output buffer: */
+ if (offset + size > size_total)
+ break;
+
ret = __copy_xstate_to_user(ubuf, src, offset, size, size_total);
if (ret)
return ret;
-
- if (offset + size >= size_total)
- break;
}

}
--
2.11.0
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