kernel.git/arch/x86/kernel/vmlinux.lds.S, branch linux-5.7.y

x86, vmlinux.lds: Page-align end of ..page_aligned sections

2020-07-29T08:19:59Z

commit de2b41be8fcccb2f5b6c480d35df590476344201 upstream. On x86-32 the idt_table with 256 entries needs only 2048 bytes. It is page-aligned, but the end of the .bss..page_aligned section is not guaranteed to be page-aligned. As a result, objects from other .bss sections may end up on the same 4k page as the idt_table, and will accidentially get mapped read-only during boot, causing unexpected page-faults when the kernel writes to them. This could be worked around by making the objects in the page aligned sections page sized, but that's wrong. Explicit sections which store only page aligned objects have an implicit guarantee that the object is alone in the page in which it is placed. That works for all objects except the last one. That's inconsistent. Enforcing page sized objects for these sections would wreckage memory sanitizers, because the object becomes artificially larger than it should be and out of bound access becomes legit. Align the end of the .bss..page_aligned and .data..page_aligned section on page-size so all objects places in these sections are guaranteed to have their own page. [ tglx: Amended changelog ] Signed-off-by: Joerg Roedel Signed-off-by: Thomas Gleixner Reviewed-by: Kees Cook Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20200721093448.10417-1-joro@8bytes.org Signed-off-by: Greg Kroah-Hartman

x86_64: Fix jiffies ODR violation

2020-06-17T14:42:48Z

commit d8ad6d39c35d2b44b3d48b787df7f3359381dcbf upstream. 'jiffies' and 'jiffies_64' are meant to alias (two different symbols that share the same address). Most architectures make the symbols alias to the same address via a linker script assignment in their arch//kernel/vmlinux.lds.S: jiffies = jiffies_64; which is effectively a definition of jiffies. jiffies and jiffies_64 are both forward declared for all architectures in include/linux/jiffies.h. jiffies_64 is defined in kernel/time/timer.c. x86_64 was peculiar in that it wasn't doing the above linker script assignment, but rather was: 1. defining jiffies in arch/x86/kernel/time.c instead via the linker script. 2. overriding the symbol jiffies_64 from kernel/time/timer.c in arch/x86/kernel/vmlinux.lds.s via 'jiffies_64 = jiffies;'. As Fangrui notes: In LLD, symbol assignments in linker scripts override definitions in object files. GNU ld appears to have the same behavior. It would probably make sense for LLD to error "duplicate symbol" but GNU ld is unlikely to adopt for compatibility reasons. This results in an ODR violation (UB), which seems to have survived thus far. Where it becomes harmful is when; 1. -fno-semantic-interposition is used: As Fangrui notes: Clang after LLVM commit 5b22bcc2b70d ("[X86][ELF] Prefer to lower MC_GlobalAddress operands to .Lfoo$local") defaults to -fno-semantic-interposition similar semantics which help -fpic/-fPIC code avoid GOT/PLT when the referenced symbol is defined within the same translation unit. Unlike GCC -fno-semantic-interposition, Clang emits such relocations referencing local symbols for non-pic code as well. This causes references to jiffies to refer to '.Ljiffies$local' when jiffies is defined in the same translation unit. Likewise, references to jiffies_64 become references to '.Ljiffies_64$local' in translation units that define jiffies_64. Because these differ from the names used in the linker script, they will not be rewritten to alias one another. 2. Full LTO Full LTO effectively treats all source files as one translation unit, causing these local references to be produced everywhere. When the linker processes the linker script, there are no longer any references to jiffies_64' anywhere to replace with 'jiffies'. And thus '.Ljiffies$local' and '.Ljiffies_64$local' no longer alias at all. In the process of porting patches enabling Full LTO from arm64 to x86_64, spooky bugs have been observed where the kernel appeared to boot, but init doesn't get scheduled. Avoid the ODR violation by matching other architectures and define jiffies only by linker script. For -fno-semantic-interposition + Full LTO, there is no longer a global definition of jiffies for the compiler to produce a local symbol which the linker script won't ensure aliases to jiffies_64. Fixes: 40747ffa5aa8 ("asmlinkage: Make jiffies visible") Reported-by: Nathan Chancellor Reported-by: Alistair Delva Debugged-by: Nick Desaulniers Debugged-by: Sami Tolvanen Suggested-by: Fangrui Song Signed-off-by: Bob Haarman Signed-off-by: Thomas Gleixner Tested-by: Sedat Dilek # build+boot on Reviewed-by: Andi Kleen Reviewed-by: Josh Poimboeuf Cc: stable@vger.kernel.org Link: https://github.com/ClangBuiltLinux/linux/issues/852 Link: https://lkml.kernel.org/r/20200602193100.229287-1-inglorion@google.com Signed-off-by: Greg Kroah-Hartman

Merge branch 'x86-build-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-03-31T17:51:12Z

Pull x86 build updates from Ingo Molnar: "A handful of updates: two linker script cleanups and a stock defconfig+allmodconfig bootability fix" * 'x86-build-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/vdso: Discard .note.gnu.property sections in vDSO x86, vmlinux.lds: Add RUNTIME_DISCARD_EXIT to generic DISCARDS x86/Kconfig: Make CMDLINE_OVERRIDE depend on non-empty CMDLINE

x86, vmlinux.lds: Add RUNTIME_DISCARD_EXIT to generic DISCARDS

2020-03-27T10:52:11Z

In the x86 kernel, .exit.text and .exit.data sections are discarded at runtime, not by the linker. Add RUNTIME_DISCARD_EXIT to generic DISCARDS and define it in the x86 kernel linker script to keep them. The sections are added before the DISCARD directive so document here only the situation explicitly as this change doesn't have any effect on the generated kernel. Also, other architectures like ARM64 will use it too so generalize the approach with the RUNTIME_DISCARD_EXIT define. [ bp: Massage and extend commit message. ] Signed-off-by: H.J. Lu Signed-off-by: Borislav Petkov Reviewed-by: Kees Cook Link: https://lkml.kernel.org/r/20200326193021.255002-1-hjl.tools@gmail.com

x86/vmlinux: Drop unneeded linker script discard of .eh_frame

2020-02-25T13:51:29Z

Now that .eh_frame sections for the files in setup.elf and realmode.elf are not generated anymore, the linker scripts don't need the special output section name /DISCARD/ any more. Remove the one in the main kernel linker script as well, since there are no .eh_frame sections already, and fix up a comment referencing .eh_frame. Update the comment in asm/dwarf2.h referring to .eh_frame so it continues to make sense, as well as being more specific. [ bp: Touch up commit message. ] Signed-off-by: Arvind Sankar Signed-off-by: Borislav Petkov Reviewed-by: Nathan Chancellor Reviewed-by: Nick Desaulniers Reviewed-by: Kees Cook Tested-by: Nathan Chancellor Link: https://lkml.kernel.org/r/20200224232129.597160-3-nivedita@alum.mit.edu

x86/vdso: Provide vdso_data offset on vvar_page

2020-01-14T11:20:57Z

VDSO support for time namespaces needs to set up a page with the same layout as VVAR. That timens page will be placed on position of VVAR page inside namespace. That page has vdso_data->seq set to 1 to enforce the slow path and vdso_data->clock_mode set to VCLOCK_TIMENS to enforce the time namespace handling path. To prepare the time namespace page the kernel needs to know the vdso_data offset. Provide arch_get_vdso_data() helper for locating vdso_data on VVAR page. Co-developed-by: Andrei Vagin Signed-off-by: Andrei Vagin Signed-off-by: Dmitry Safonov Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20191112012724.250792-22-dima@arista.com

x86/vmlinux: Use INT3 instead of NOP for linker fill bytes

2019-11-04T18:10:08Z

Instead of using 0x90 (NOP) to fill bytes between functions, which makes it easier to sloppily target functions in function pointer overwrite attacks, fill with 0xCC (INT3) to force a trap. Also drop the space between "=" and the value to better match the binutils documentation https://sourceware.org/binutils/docs/ld/Output-Section-Fill.html#Output-Section-Fill Example "objdump -d" before: ... ffffffff810001e0 : ffffffff810001e0: 48 8b 25 e1 b1 51 01 mov 0x151b1e1(%rip),%rsp # ffffffff8251b3c8 ffffffff810001e7: e9 d5 fe ff ff jmpq ffffffff810000c1 ffffffff810001ec: 90 nop ffffffff810001ed: 90 nop ffffffff810001ee: 90 nop ffffffff810001ef: 90 nop ffffffff810001f0 <__startup_64>: ... After: ... ffffffff810001e0 : ffffffff810001e0: 48 8b 25 41 79 53 01 mov 0x1537941(%rip),%rsp # ffffffff82537b28 ffffffff810001e7: e9 d5 fe ff ff jmpq ffffffff810000c1 ffffffff810001ec: cc int3 ffffffff810001ed: cc int3 ffffffff810001ee: cc int3 ffffffff810001ef: cc int3 ffffffff810001f0 <__startup_64>: ... Signed-off-by: Kees Cook Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Dave Hansen Cc: Heiko Carstens Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: linux-alpha@vger.kernel.org Cc: linux-arch@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-c6x-dev@linux-c6x.org Cc: linux-ia64@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-s390@vger.kernel.org Cc: Michael Ellerman Cc: Michal Simek Cc: Rick Edgecombe Cc: Ross Zwisler Cc: Segher Boessenkool Cc: Thomas Gleixner Cc: Thomas Lendacky Cc: Will Deacon Cc: x86-ml Cc: Yoshinori Sato Link: https://lkml.kernel.org/r/20191029211351.13243-30-keescook@chromium.org

x86/vmlinux: Move EXCEPTION_TABLE to RO_DATA segment

2019-11-04T16:55:02Z

The exception table was needlessly marked executable. In preparation for execute-only memory, move the table into the RO_DATA segment via the new macro that can be used by any architectures that want to make a similar consolidation. Signed-off-by: Kees Cook Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Dave Hansen Cc: Heiko Carstens Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: linux-alpha@vger.kernel.org Cc: linux-arch@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-c6x-dev@linux-c6x.org Cc: linux-ia64@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-s390@vger.kernel.org Cc: Michael Ellerman Cc: Michal Simek Cc: Rick Edgecombe Cc: Ross Zwisler Cc: Segher Boessenkool Cc: Thomas Gleixner Cc: Thomas Lendacky Cc: Will Deacon Cc: x86-ml Cc: Yoshinori Sato Link: https://lkml.kernel.org/r/20191029211351.13243-17-keescook@chromium.org

x86/vmlinux: Actually use _etext for the end of the text segment

2019-11-04T16:54:16Z

Various calculations are using the end of the exception table (which does not need to be executable) as the end of the text segment. Instead, in preparation for moving the exception table into RO_DATA, move _etext after the exception table and update the calculations. Signed-off-by: Kees Cook Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Dave Hansen Cc: Heiko Carstens Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: linux-alpha@vger.kernel.org Cc: linux-arch@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-c6x-dev@linux-c6x.org Cc: linux-ia64@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-s390@vger.kernel.org Cc: Michael Ellerman Cc: Michal Simek Cc: Nick Desaulniers Cc: Peter Zijlstra Cc: Rick Edgecombe Cc: Ross Zwisler Cc: Segher Boessenkool Cc: Thomas Gleixner Cc: Thomas Lendacky Cc: Will Deacon Cc: x86-ml Cc: Yoshinori Sato Link: https://lkml.kernel.org/r/20191029211351.13243-16-keescook@chromium.org

vmlinux.lds.h: Move NOTES into RO_DATA

2019-11-04T14:34:41Z

The .notes section should be non-executable read-only data. As such, move it to the RO_DATA macro instead of being per-architecture defined. Signed-off-by: Kees Cook Signed-off-by: Borislav Petkov Acked-by: Heiko Carstens # s390 Cc: Andy Lutomirski Cc: Arnd Bergmann Cc: Dave Hansen Cc: linux-alpha@vger.kernel.org Cc: linux-arch@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-c6x-dev@linux-c6x.org Cc: linux-ia64@vger.kernel.org Cc: linux-s390@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: Michael Ellerman Cc: Michal Simek Cc: Rick Edgecombe Cc: Segher Boessenkool Cc: Will Deacon Cc: x86-ml Cc: Yoshinori Sato Link: https://lkml.kernel.org/r/20191029211351.13243-11-keescook@chromium.org