diff options
| author | Topi Miettinen <toiwoton@gmail.com> | 2016-10-26 18:52:53 +0300 |
|---|---|---|
| committer | Topi Miettinen <toiwoton@gmail.com> | 2016-10-26 18:59:14 +0300 |
| commit | d2ffa389b8112282be1633bb4638f6f47e159299 (patch) | |
| tree | 302dea53e6baa7c26521de3da308ab77b3a5e034 | |
| parent | d4a48671bc453ead3cff911a0dfcc16ce5538072 (diff) | |
seccomp: also block shmat(..., SHM_EXEC) for MemoryDenyWriteExecute
shmat(..., SHM_EXEC) can be used to create writable and executable
memory, so let's block it when MemoryDenyWriteExecute is set.
| -rw-r--r-- | man/systemd.exec.xml | 11 | ||||
| -rw-r--r-- | src/core/execute.c | 11 |
2 files changed, 18 insertions, 4 deletions
diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml index dbe4594730..f9a15d8db0 100644 --- a/man/systemd.exec.xml +++ b/man/systemd.exec.xml @@ -1516,12 +1516,15 @@ <term><varname>MemoryDenyWriteExecute=</varname></term> <listitem><para>Takes a boolean argument. If set, attempts to create memory mappings that are writable and - executable at the same time, or to change existing memory mappings to become executable are prohibited. + executable at the same time, or to change existing memory mappings to become executable, or mapping shared memory + segments as executable are prohibited. Specifically, a system call filter is added that rejects <citerefentry><refentrytitle>mmap</refentrytitle><manvolnum>2</manvolnum></citerefentry> - system calls with both <constant>PROT_EXEC</constant> and <constant>PROT_WRITE</constant> set - and <citerefentry><refentrytitle>mprotect</refentrytitle><manvolnum>2</manvolnum></citerefentry> - system calls with <constant>PROT_EXEC</constant> set. Note that this option is incompatible with programs + system calls with both <constant>PROT_EXEC</constant> and <constant>PROT_WRITE</constant> set, + <citerefentry><refentrytitle>mprotect</refentrytitle><manvolnum>2</manvolnum></citerefentry> + system calls with <constant>PROT_EXEC</constant> set and + <citerefentry><refentrytitle>shmat</refentrytitle><manvolnum>2</manvolnum></citerefentry> + system calls with <constant>SHM_EXEC</constant> set. Note that this option is incompatible with programs that generate program code dynamically at runtime, such as JIT execution engines, or programs compiled making use of the code "trampoline" feature of various C compilers. This option improves service security, as it makes harder for software exploits to change running code dynamically. diff --git a/src/core/execute.c b/src/core/execute.c index 5e7d7c25d7..7b42ac7bdc 100644 --- a/src/core/execute.c +++ b/src/core/execute.c @@ -29,8 +29,10 @@ #include <sys/mman.h> #include <sys/personality.h> #include <sys/prctl.h> +#include <sys/shm.h> #include <sys/socket.h> #include <sys/stat.h> +#include <sys/types.h> #include <sys/un.h> #include <unistd.h> #include <utmpx.h> @@ -1394,6 +1396,15 @@ static int apply_memory_deny_write_execute(const Unit* u, const ExecContext *c) if (r < 0) goto finish; + r = seccomp_rule_add( + seccomp, + SCMP_ACT_ERRNO(EPERM), + SCMP_SYS(shmat), + 1, + SCMP_A2(SCMP_CMP_MASKED_EQ, SHM_EXEC, SHM_EXEC)); + if (r < 0) + goto finish; + r = seccomp_load(seccomp); finish: |