copy_xstate_to_kernel(): don't leave parts of destination uninitialized

commit 9e4636545933131de15e1ecd06733538ae939b2f upstream.

copy the corresponding pieces of init_fpstate into the gaps instead.

Cc: stable@kernel.org
Tested-by: Alexander Potapenko <glider@google.com>
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 87a57b7642d3673420b272fec0f442b9baf76414..61c2fb8b1f8ef2d2e5cb333be29d3c183d938105 100644 (file)
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -964,18 +964,31 @@ static inline bool xfeatures_mxcsr_quirk(u64 xfeatures)
        return true;
 }
 
-/*
- * This is similar to user_regset_copyout(), but will not add offset to
- * the source data pointer or increment pos, count, kbuf, and ubuf.
- */
-static inline void
-__copy_xstate_to_kernel(void *kbuf, const void *data,
-                       unsigned int offset, unsigned int size, unsigned int size_total)
+static void fill_gap(unsigned to, void **kbuf, unsigned *pos, unsigned *count)
 {
-       if (offset < size_total) {
-               unsigned int copy = min(size, size_total - offset);
+       if (*pos < to) {
+               unsigned size = to - *pos;
+
+               if (size > *count)
+                       size = *count;
+               memcpy(*kbuf, (void *)&init_fpstate.xsave + *pos, size);
+               *kbuf += size;
+               *pos += size;
+               *count -= size;
+       }
+}
 
-               memcpy(kbuf + offset, data, copy);
+static void copy_part(unsigned offset, unsigned size, void *from,
+                       void **kbuf, unsigned *pos, unsigned *count)
+{
+       fill_gap(offset, kbuf, pos, count);
+       if (size > *count)
+               size = *count;
+       if (size) {
+               memcpy(*kbuf, from, size);
+               *kbuf += size;
+               *pos += size;
+               *count -= size;
        }
 }
 
@@ -988,8 +1001,9 @@ __copy_xstate_to_kernel(void *kbuf, const void *data,
  */
 int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int offset_start, unsigned int size_total)
 {
-       unsigned int offset, size;
        struct xstate_header header;
+       const unsigned off_mxcsr = offsetof(struct fxregs_state, mxcsr);
+       unsigned count = size_total;
        int i;
 
        /*
@@ -1005,46 +1019,42 @@ int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int of
        header.xfeatures = xsave->header.xfeatures;
        header.xfeatures &= ~XFEATURE_MASK_SUPERVISOR;
 
+       if (header.xfeatures & XFEATURE_MASK_FP)
+               copy_part(0, off_mxcsr,
+                         &xsave->i387, &kbuf, &offset_start, &count);
+       if (header.xfeatures & (XFEATURE_MASK_SSE | XFEATURE_MASK_YMM))
+               copy_part(off_mxcsr, MXCSR_AND_FLAGS_SIZE,
+                         &xsave->i387.mxcsr, &kbuf, &offset_start, &count);
+       if (header.xfeatures & XFEATURE_MASK_FP)
+               copy_part(offsetof(struct fxregs_state, st_space), 128,
+                         &xsave->i387.st_space, &kbuf, &offset_start, &count);
+       if (header.xfeatures & XFEATURE_MASK_SSE)
+               copy_part(xstate_offsets[XFEATURE_MASK_SSE], 256,
+                         &xsave->i387.xmm_space, &kbuf, &offset_start, &count);
+       /*
+        * Fill xsave->i387.sw_reserved value for ptrace frame:
+        */
+       copy_part(offsetof(struct fxregs_state, sw_reserved), 48,
+                 xstate_fx_sw_bytes, &kbuf, &offset_start, &count);
        /*
         * Copy xregs_state->header:
         */
-       offset = offsetof(struct xregs_state, header);
-       size = sizeof(header);
-
-       __copy_xstate_to_kernel(kbuf, &header, offset, size, size_total);
+       copy_part(offsetof(struct xregs_state, header), sizeof(header),
+                 &header, &kbuf, &offset_start, &count);
 
-       for (i = 0; i < XFEATURE_MAX; i++) {
+       for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
                /*
                 * Copy only in-use xstates:
                 */
                if ((header.xfeatures >> i) & 1) {
                        void *src = __raw_xsave_addr(xsave, 1 << 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;
-
-                       __copy_xstate_to_kernel(kbuf, src, offset, size, size_total);
+                       copy_part(xstate_offsets[i], xstate_sizes[i],
+                                 src, &kbuf, &offset_start, &count);
                }
 
        }
-
-       if (xfeatures_mxcsr_quirk(header.xfeatures)) {
-               offset = offsetof(struct fxregs_state, mxcsr);
-               size = MXCSR_AND_FLAGS_SIZE;
-               __copy_xstate_to_kernel(kbuf, &xsave->i387.mxcsr, offset, size, size_total);
-       }
-
-       /*
-        * Fill xsave->i387.sw_reserved value for ptrace frame:
-        */
-       offset = offsetof(struct fxregs_state, sw_reserved);
-       size = sizeof(xstate_fx_sw_bytes);
-
-       __copy_xstate_to_kernel(kbuf, xstate_fx_sw_bytes, offset, size, size_total);
+       fill_gap(size_total, &kbuf, &offset_start, &count);
 
        return 0;
 }