Commit ac7b3421 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'core_core_updates_for_5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull READ_IMPLIES_EXEC changes from Borislav Petkov:
 "Split the old READ_IMPLIES_EXEC workaround from executable
  PT_GNU_STACK now that toolchains long support PT_GNU_STACK marking and
  there's no need anymore to force modern programs into having all its
  user mappings executable instead of only the stack and the PROT_EXEC
  ones.

  Disable that automatic READ_IMPLIES_EXEC forcing on x86-64 and
  arm64.

  Add tables documenting how READ_IMPLIES_EXEC is handled on x86-64, arm
  and arm64.

  By Kees Cook"

* tag 'core_core_updates_for_5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  arm64/elf: Disable automatic READ_IMPLIES_EXEC for 64-bit address spaces
  arm32/64/elf: Split READ_IMPLIES_EXEC from executable PT_GNU_STACK
  arm32/64/elf: Add tables to document READ_IMPLIES_EXEC
  x86/elf: Disable automatic READ_IMPLIES_EXEC on 64-bit
  x86/elf: Split READ_IMPLIES_EXEC from executable PT_GNU_STACK
  x86/elf: Add table to document READ_IMPLIES_EXEC
parents 7ae77150 6e0d6ac5

arch/arm/kernel/elf.c

+23 −4
Original line number Diff line number Diff line
@@ -78,13 +78,32 @@ void elf_set_personality(const struct elf32_hdr *x) 
EXPORT_SYMBOL(elf_set_personality);



/*

 * Set READ_IMPLIES_EXEC if:

 *  - the binary requires an executable stack

 *  - we're running on a CPU which doesn't support NX.

 * An executable for which elf_read_implies_exec() returns TRUE will

 * have the READ_IMPLIES_EXEC personality flag set automatically.

 *

 * The decision process for determining the results are:

 *

 *                 CPU: | lacks NX*  | has NX     |

 * ELF:                 |            |            |

 * ---------------------|------------|------------|

 * missing PT_GNU_STACK | exec-all   | exec-all   |

 * PT_GNU_STACK == RWX  | exec-all   | exec-stack |

 * PT_GNU_STACK == RW   | exec-all   | exec-none  |

 *

 *  exec-all  : all PROT_READ user mappings are executable, except when

 *              backed by files on a noexec-filesystem.

 *  exec-none : only PROT_EXEC user mappings are executable.

 *  exec-stack: only the stack and PROT_EXEC user mappings are executable.

 *

 *  *this column has no architectural effect: NX markings are ignored by

 *   hardware, but may have behavioral effects when "wants X" collides with

 *   "cannot be X" constraints in memory permission flags, as in

 *   https://lkml.kernel.org/r/20190418055759.GA3155@mellanox.com

 *

 */

int arm_elf_read_implies_exec(int executable_stack)

{

	if (executable_stack != EXSTACK_DISABLE_X)

	if (executable_stack == EXSTACK_DEFAULT)

		return 1;

	if (cpu_architecture() < CPU_ARCH_ARMv6)

		return 1;

arch/arm64/include/asm/elf.h

+22 −1
Original line number Diff line number Diff line
@@ -96,7 +96,28 @@ 
 */

#define elf_check_arch(x)		((x)->e_machine == EM_AARCH64)



#define elf_read_implies_exec(ex,stk)	(stk != EXSTACK_DISABLE_X)

/*

 * An executable for which elf_read_implies_exec() returns TRUE will

 * have the READ_IMPLIES_EXEC personality flag set automatically.

 *

 * The decision process for determining the results are:

 *

 *                CPU*: | arm32      | arm64      |

 * ELF:                 |            |            |

 * ---------------------|------------|------------|

 * missing PT_GNU_STACK | exec-all   | exec-none  |

 * PT_GNU_STACK == RWX  | exec-stack | exec-stack |

 * PT_GNU_STACK == RW   | exec-none  | exec-none  |

 *

 *  exec-all  : all PROT_READ user mappings are executable, except when

 *              backed by files on a noexec-filesystem.

 *  exec-none : only PROT_EXEC user mappings are executable.

 *  exec-stack: only the stack and PROT_EXEC user mappings are executable.

 *

 *  *all arm64 CPUs support NX, so there is no "lacks NX" column.

 *

 */

#define compat_elf_read_implies_exec(ex, stk)	(stk == EXSTACK_DEFAULT)



#define CORE_DUMP_USE_REGSET

#define ELF_EXEC_PAGESIZE	PAGE_SIZE

arch/x86/include/asm/elf.h

+21 −1
Original line number Diff line number Diff line
@@ -281,9 +281,29 @@ extern u32 elf_hwcap2; 
/*

 * An executable for which elf_read_implies_exec() returns TRUE will

 * have the READ_IMPLIES_EXEC personality flag set automatically.

 *

 * The decision process for determining the results are:

 *

 *                 CPU: | lacks NX*  | has NX, ia32     | has NX, x86_64 |

 * ELF:                 |            |                  |                |

 * ---------------------|------------|------------------|----------------|

 * missing PT_GNU_STACK | exec-all   | exec-all         | exec-none      |

 * PT_GNU_STACK == RWX  | exec-stack | exec-stack       | exec-stack     |

 * PT_GNU_STACK == RW   | exec-none  | exec-none        | exec-none      |

 *

 *  exec-all  : all PROT_READ user mappings are executable, except when

 *              backed by files on a noexec-filesystem.

 *  exec-none : only PROT_EXEC user mappings are executable.

 *  exec-stack: only the stack and PROT_EXEC user mappings are executable.

 *

 *  *this column has no architectural effect: NX markings are ignored by

 *   hardware, but may have behavioral effects when "wants X" collides with

 *   "cannot be X" constraints in memory permission flags, as in

 *   https://lkml.kernel.org/r/20190418055759.GA3155@mellanox.com

 *

 */

#define elf_read_implies_exec(ex, executable_stack)	\

	(executable_stack != EXSTACK_DISABLE_X)

	(mmap_is_ia32() && executable_stack == EXSTACK_DEFAULT)



struct task_struct;

fs/compat_binfmt_elf.c

+5 −0
Original line number Diff line number Diff line
@@ -117,6 +117,11 @@ 
#define	arch_setup_additional_pages compat_arch_setup_additional_pages

#endif



#ifdef	compat_elf_read_implies_exec

#undef	elf_read_implies_exec

#define	elf_read_implies_exec compat_elf_read_implies_exec

#endif



/*

 * Rename a few of the symbols that binfmt_elf.c will define.

 * These are all local so the names don't really matter, but it