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allow mprotect(2) with PROT_(READ|WRITE|NONE) only 

Used by some hardened heap allocators. Requested by Yegor
Timoshenko in https://github.com/openssh/openssh-portable/pull/142
This commit is contained in:
Damien Miller 2019-08-23 10:08:48 +10:00
parent e3b6c966b7
commit f6906f9bf1
1 changed files with 24 additions and 2 deletions
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26
sandbox-seccomp-filter.c
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@ -42,6 +42,7 @@
#include <sys/types.h>
#include <sys/resource.h>
#include <sys/prctl.h>
#include <sys/mman.h>
#include <linux/net.h>
#include <linux/audit.h>
@ -95,12 +96,12 @@
BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW)
#define SC_ALLOW_ARG(_nr, _arg_nr, _arg_val) \
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 6), \
/* load and test first syscall argument, low word */ \
/* load and test syscall argument, low word */ \
BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_LO_OFFSET), \
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, \
((_arg_val) & 0xFFFFFFFF), 0, 3), \
/* load and test first syscall argument, high word */ \
/* load and test syscall argument, high word */ \
BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_HI_OFFSET), \
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, \
@ -109,6 +110,24 @@
/* reload syscall number; all rules expect it in accumulator */ \
BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
offsetof(struct seccomp_data, nr))
/* Allow if syscall argument contains only values in mask */
#define SC_ALLOW_ARG_MASK(_nr, _arg_nr, _arg_mask) \
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (_nr), 0, 8), \
/* load, mask and test syscall argument, low word */ \
BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_LO_OFFSET), \
BPF_STMT(BPF_ALU+BPF_AND+BPF_K, ~((_arg_mask) & 0xFFFFFFFF)), \
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0, 0, 4), \
/* load, mask and test syscall argument, high word */ \
BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
offsetof(struct seccomp_data, args[(_arg_nr)]) + ARG_HI_OFFSET), \
BPF_STMT(BPF_ALU+BPF_AND+BPF_K, \
~(((uint32_t)((uint64_t)(_arg_mask) >> 32)) & 0xFFFFFFFF)), \
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0, 0, 1), \
BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), \
/* reload syscall number; all rules expect it in accumulator */ \
BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
offsetof(struct seccomp_data, nr))
/* Syscall filtering set for preauth. */
static const struct sock_filter preauth_insns[] = {
@ -202,6 +221,9 @@ static const struct sock_filter preauth_insns[] = {
#ifdef __NR_mmap2
SC_ALLOW(__NR_mmap2),
#endif
#ifdef __NR_mprotect
SC_ALLOW_ARG_MASK(__NR_mprotect, 2, PROT_READ|PROT_WRITE|PROT_NONE),
#endif
#ifdef __NR_mremap
SC_ALLOW(__NR_mremap),
#endif