From: Alexander Potapenko <glider@google.com> To: Al Viro <viro@zeniv.linux.org.uk> Cc: Kees Cook <keescook@chromium.org>, Andrew Morton <akpm@linux-foundation.org>, Alexey Dobriyan <adobriyan@gmail.com>, LKML <linux-kernel@vger.kernel.org>, sunhaoyl@outlook.com, "the arch/x86 maintainers" <x86@kernel.org> Subject: Re: [PATCH] fs/binfmt_elf.c: allocate initialized memory in fill_thread_core_info() Date: Wed, 27 May 2020 14:08:34 +0200 [thread overview] Message-ID: <CAG_fn=Xvhdjhd97ChesvXScGhCC-kVp0yxT-W5L9WzaF2_4UjA@mail.gmail.com> (raw) In-Reply-To: <20200526223817.GA3819674@ZenIV.linux.org.uk> On Wed, May 27, 2020 at 12:38 AM Al Viro <viro@zeniv.linux.org.uk> wrote: > > On Mon, May 25, 2020 at 12:45:35AM +0100, Al Viro wrote: > > On Wed, May 13, 2020 at 04:33:49AM +0100, Al Viro wrote: > > > > > FWIW, what I'm going to do is > > > * make all callers of copy_regset_to_user() pass 0 as pos > > > (there are very few exceptions - one on arm64, three on sparc32 > > > and five on sparc64; I hadn't dealt with arm64 one yet, but all > > > cases on sparc are handled) > > > > [snip] > > > > Any of that would be easy to backport, though. Several questions > > regaring XSAVE and friends: > > > > * do we ever run on XSAVE/XSAVES-capable hardware with XFEATURE_FP > > turned off? > > > > * is it possible for x86 to have gaps between the state components > > area as reported by CPUID 0x0d? IOW, can area for feature 2 > > (XFEATURE_YMM) to start *not* at 0x200 and can area for N start > > not right after the end of area for N-1 for some N > 2? > > > > I think I have an easy-to-backport solution, but I'm really confused > > about XFEATURE_FP situation... > > Folks, could you test the following? > > copy_xstate_to_kernel(): don't leave parts of destination uninitialized > > copy the corresponding pieces of init_fpstate into the gaps instead. > > Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Alexander Potapenko <glider@google.com> > --- > diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c > index 32b153d38748..6a54e83d5589 100644 > --- a/arch/x86/kernel/fpu/xstate.c > +++ b/arch/x86/kernel/fpu/xstate.c > @@ -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; > + > + 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; > } > } > > @@ -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_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, 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; > } -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
next prev parent reply other threads:[~2020-05-27 12:09 UTC|newest] Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-04-19 10:08 glider 2020-04-19 10:10 ` Alexander Potapenko 2020-04-20 22:33 ` Andrew Morton 2020-04-20 22:41 ` Kees Cook 2020-04-21 3:42 ` Al Viro 2020-04-21 8:14 ` Alexander Potapenko 2020-05-12 1:09 ` Al Viro 2020-05-12 3:44 ` Al Viro 2020-05-12 8:20 ` Alexander Potapenko 2020-05-13 3:33 ` Al Viro 2020-05-24 23:45 ` Al Viro 2020-05-26 22:38 ` Al Viro 2020-05-27 12:08 ` Alexander Potapenko [this message] 2020-05-27 19:04 ` Borislav Petkov 2020-05-27 19:53 ` Al Viro 2020-05-27 20:09 ` Borislav Petkov 2020-04-21 12:54 ` Alexander Potapenko 2020-04-21 15:09 ` Jann Horn 2020-04-21 16:04 ` Yu-cheng Yu 2020-04-21 16:16 ` Jann Horn 2020-04-21 16:26 ` Yu-cheng Yu 2020-04-21 20:20 ` Kees Cook 2020-04-21 8:06 ` Alexander Potapenko 2020-05-27 21:55 ` Kees Cook 2020-04-21 8:00 ` Alexander Potapenko
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