b272ed230e
The "ground truth" stack protector cookie value is kept in a global variable, and loaded in every function prologue and epilogue to store it into resp. compare it with the stack slot holding the cookie. If the comparison fails, the program aborts, and this might occur spuriously when the global variable changes values between the entry and exit of a function. This implies that assigning the global variable at boot should not involve any instrumented function calls, unless special care is taken to ensure that the live call stack is synchronized, which is non-trivial. So avoid any function calls, including grub_memcpy(), which is unnecessary given that the stack cookie is always a suitably aligned variable of the native word size. While at it, leave the last byte 0x0 to avoid inadvertent unbounded strings on the stack. Note that the use of __attribute__((optimize)) is described as unsuitable for production use in the GCC documentation, so let's drop this as well now that it is no longer needed. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Glenn Washburn <development@efficientek.com> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
47 lines
1.6 KiB
C
47 lines
1.6 KiB
C
/*
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* GRUB -- GRand Unified Bootloader
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* Copyright (C) 2021 Free Software Foundation, Inc.
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*
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* GRUB is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GRUB is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef GRUB_STACK_PROTECTOR_H
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#define GRUB_STACK_PROTECTOR_H 1
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#include <grub/symbol.h>
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#include <grub/types.h>
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#ifdef GRUB_STACK_PROTECTOR
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extern grub_addr_t EXPORT_VAR (__stack_chk_guard);
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extern void __attribute__ ((noreturn)) EXPORT_FUNC (__stack_chk_fail) (void);
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#if defined(_WIN64) && !defined(__CYGWIN__) /* MinGW, Windows 64-bit target. */
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static grub_addr_t __attribute__ ((weakref("__stack_chk_guard"))) EXPORT_VAR (_stack_chk_guard);
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static void __attribute__ ((noreturn, weakref("__stack_chk_fail"))) EXPORT_FUNC (_stack_chk_fail) (void);
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#endif
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extern grub_addr_t grub_stack_protector_init (void);
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static inline __attribute__((__always_inline__))
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void grub_update_stack_guard (void)
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{
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grub_addr_t guard;
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guard = grub_stack_protector_init ();
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if (guard)
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__stack_chk_guard = guard;
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}
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#endif
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#endif /* GRUB_STACK_PROTECTOR_H */
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