[Qemu-devel] [PATCH v3] Add seccomp argument filters for madvise, shmget, and shmctl

[Namsun Ch'o]

Signed-off-by: Namsun Ch'o <address@hidden>
---
Changes so far:
v1
 - Created argument filters for the madvise, shmget, and shmctl 
syscalls.
v1 -> v2
 - Added 5 new madvise flags which were present in the source code but 
not in
   the strace which I generated.
 - Added IP_CREAT|0600 to shmget, which Daniel Berrange pointed out was
   present in GTK2, which QEMU uses but does not call directly.
v2 -> v3
 - Replaced include asm/mman-common.h with sys/mman.h which is more 
proper.
 - Fixed a stupid typo where I had IP_CREAT instead of IPC_CREAT.
 - Removed the comma on the last entry of the madvise_flags array.
 - Removed one madvise flag (MADV_INVALID) which doesn't exist, 
apparently.
 qemu-seccomp.c | 58 
+++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 55 insertions(+), 3 deletions(-)

diff --git a/qemu-seccomp.c b/qemu-seccomp.c
index 33644a4..e7a54e8 100644
--- a/qemu-seccomp.c
+++ b/qemu-seccomp.c
@@ -14,6 +14,8 @@
  */
 #include <stdio.h>
 #include <seccomp.h>
+#include <linux/ipc.h>
+#include <sys/mman.h>
 #include "sysemu/seccomp.h"

 struct QemuSeccompSyscall {
@@ -105,7 +107,6 @@ static const struct QemuSeccompSyscall 
seccomp_whitelist[] = {
     { SCMP_SYS(rt_sigreturn), 245 },
     { SCMP_SYS(sync), 245 },
     { SCMP_SYS(pread64), 245 },
-    { SCMP_SYS(madvise), 245 },
     { SCMP_SYS(set_robust_list), 245 },
     { SCMP_SYS(lseek), 245 },
     { SCMP_SYS(pselect6), 245 },
@@ -224,11 +225,9 @@ static const struct QemuSeccompSyscall 
seccomp_whitelist[] = {
     { SCMP_SYS(arch_prctl), 240 },
     { SCMP_SYS(mkdir), 240 },
     { SCMP_SYS(fchmod), 240 },
-    { SCMP_SYS(shmget), 240 },
     { SCMP_SYS(shmat), 240 },
     { SCMP_SYS(shmdt), 240 },
     { SCMP_SYS(timerfd_create), 240 },
-    { SCMP_SYS(shmctl), 240 },
     { SCMP_SYS(mlockall), 240 },
     { SCMP_SYS(mlock), 240 },
     { SCMP_SYS(munlock), 240 },
@@ -265,6 +264,59 @@ int seccomp_start(void)
         }
     }

+    /* madvise */
+    static const int madvise_flags[] = {
+        MADV_DODUMP,
+        MADV_DONTDUMP,
+        MADV_UNMERGEABLE,
+        MADV_WILLNEED,
+        MADV_DONTFORK,
+        MADV_DONTNEED,
+        MADV_HUGEPAGE,
+        MADV_MERGEABLE
+    };
+    for (i = 0; i < ARRAY_SIZE(madvise_flags); i++) {
+        rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(madvise), 
1,
+            SCMP_A2(SCMP_CMP_EQ, madvise_flags[i]));
+        if (rc < 0) {
+            goto seccomp_return;
+        }
+    }
+    rc = seccomp_syscall_priority(ctx, SCMP_SYS(madvise), 245);
+    if (rc < 0) {
+        goto seccomp_return;
+    }
+
+    /* shmget */
+    rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(shmget), 2,
+        SCMP_A0(SCMP_CMP_EQ, IPC_PRIVATE),
+        SCMP_A2(SCMP_CMP_EQ, IPC_CREAT|0777));
+    if (rc < 0) {
+        goto seccomp_return;
+    }
+    rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(shmget), 2,
+        SCMP_A0(SCMP_CMP_EQ, IPC_PRIVATE),
+        SCMP_A2(SCMP_CMP_EQ, IPC_CREAT|0600));
+    if (rc < 0) {
+        goto seccomp_return;
+    }
+    rc = seccomp_syscall_priority(ctx, SCMP_SYS(shmget), 240);
+    if (rc < 0) {
+        goto seccomp_return;
+    }
+
+    /* shmctl */
+    rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(shmctl), 2,
+        SCMP_A1(SCMP_CMP_EQ, IPC_RMID),
+        SCMP_A2(SCMP_CMP_EQ, 0));
+    if (rc < 0) {
+        goto seccomp_return;
+    }
+    rc = seccomp_syscall_priority(ctx, SCMP_SYS(shmctl), 240);
+    if (rc < 0) {
+        goto seccomp_return;
+    }
+
     rc = seccomp_load(ctx);

   seccomp_return: