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

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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>
This commit is contained in:
Al Viro 2020-05-26 18:39:49 -04:00
parent 4e89b72104
commit 9e46365459
1 changed files with 48 additions and 38 deletions
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86
arch/x86/kernel/fpu/xstate.c
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@ -957,18 +957,31 @@ 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;
memcpy(kbuf + offset, data, copy);
if (size > *count)
size = *count;
memcpy(*kbuf, (void *)&init_fpstate.xsave + *pos, size);
*kbuf += size;
*pos += size;
*count -= size;
}
}
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;
}
}
@ -981,8 +994,9 @@ __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;
/*
@ -998,46 +1012,42 @@ 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_part(offsetof(struct xregs_state, header), sizeof(header),
&header, &kbuf, &offset_start, &count);
__copy_xstate_to_kernel(kbuf, &header, offset, size, size_total);
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, 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;
}