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5cec93c216
There's a fair amount of code in the vsyscall page. It contains a syscall instruction (in the gettimeofday fallback) and who knows what will happen if an exploit jumps into the middle of some other code. Reduce the risk by replacing the vsyscalls with short magic incantations that cause the kernel to emulate the real vsyscalls. These incantations are useless if entered in the middle. This causes vsyscalls to be a little more expensive than real syscalls. Fortunately sensible programs don't use them. The only exception is time() which is still called by glibc through the vsyscall - but calling time() millions of times per second is not sensible. glibc has this fixed in the development tree. This patch is not perfect: the vread_tsc and vread_hpet functions are still at a fixed address. Fixing that might involve making alternative patching work in the vDSO. Signed-off-by: Andy Lutomirski <luto@mit.edu> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jesper Juhl <jj@chaosbits.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Jan Beulich <JBeulich@novell.com> Cc: richard -rw- weinberger <richard.weinberger@gmail.com> Cc: Mikael Pettersson <mikpe@it.uu.se> Cc: Andi Kleen <andi@firstfloor.org> Cc: Brian Gerst <brgerst@gmail.com> Cc: Louis Rilling <Louis.Rilling@kerlabs.com> Cc: Valdis.Kletnieks@vt.edu Cc: pageexec@freemail.hu Link: http://lkml.kernel.org/r/e64e1b3c64858820d12c48fa739efbd1485e79d5.1307292171.git.luto@mit.edu [ Removed the CONFIG option - it's simpler to just do it unconditionally. Tidied up the code as well. ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
53 lines
897 B
C
53 lines
897 B
C
#ifndef _LINUX_SECCOMP_H
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#define _LINUX_SECCOMP_H
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#ifdef CONFIG_SECCOMP
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#include <linux/thread_info.h>
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#include <asm/seccomp.h>
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typedef struct { int mode; } seccomp_t;
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extern void __secure_computing(int);
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static inline void secure_computing(int this_syscall)
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{
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if (unlikely(test_thread_flag(TIF_SECCOMP)))
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__secure_computing(this_syscall);
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}
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extern long prctl_get_seccomp(void);
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extern long prctl_set_seccomp(unsigned long);
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static inline int seccomp_mode(seccomp_t *s)
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{
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return s->mode;
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}
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#else /* CONFIG_SECCOMP */
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#include <linux/errno.h>
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typedef struct { } seccomp_t;
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#define secure_computing(x) do { } while (0)
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static inline long prctl_get_seccomp(void)
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{
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return -EINVAL;
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}
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static inline long prctl_set_seccomp(unsigned long arg2)
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{
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return -EINVAL;
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}
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static inline int seccomp_mode(seccomp_t *s)
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{
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return 0;
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}
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#endif /* CONFIG_SECCOMP */
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#endif /* _LINUX_SECCOMP_H */
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