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authorPaul Moore <pmoore@redhat.com>2014-02-28 07:23:24 -0500
committerPaul Moore <pmoore@redhat.com>2014-02-28 07:23:24 -0500
commit0909c0ae999c325b9d34c6f4710f40730ae3bc24 (patch)
tree60bbe1ec3ac48a1263d0769241c268b3a3b3ecca
parent81c94e76ce8e14a487bca210b3fd92ca661516ac (diff)
selinux: put the mmap() DAC controls before the MAC controls
It turns out that doing the SELinux MAC checks for mmap() before the DAC checks was causing users and the SELinux policy folks headaches as users were seeing a lot of SELinux AVC denials for the memprotect:mmap_zero permission that would have also been denied by the normal DAC capability checks (CAP_SYS_RAWIO). Example: # cat mmap_test.c #include <stdlib.h> #include <stdio.h> #include <errno.h> #include <sys/mman.h> int main(int argc, char *argv[]) { int rc; void *mem; mem = mmap(0x0, 4096, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0); if (mem == MAP_FAILED) return errno; printf("mem = %p\n", mem); munmap(mem, 4096); return 0; } # gcc -g -O0 -o mmap_test mmap_test.c # ./mmap_test mem = (nil) # ausearch -m AVC | grep mmap_zero type=AVC msg=audit(...): avc: denied { mmap_zero } for pid=1025 comm="mmap_test" scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=memprotect This patch corrects things so that when the above example is run by a user without CAP_SYS_RAWIO the SELinux AVC is no longer generated as the DAC capability check fails before the SELinux permission check. Signed-off-by: Paul Moore <pmoore@redhat.com> Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
-rw-r--r--security/selinux/hooks.c20
1 files changed, 8 insertions, 12 deletions
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 4b34847208cc..a3230de656e4 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3204,24 +3204,20 @@ error:
static int selinux_mmap_addr(unsigned long addr)
{
- int rc = 0;
- u32 sid = current_sid();
+ int rc;
+
+ /* do DAC check on address space usage */
+ rc = cap_mmap_addr(addr);
+ if (rc)
+ return rc;
- /*
- * notice that we are intentionally putting the SELinux check before
- * the secondary cap_file_mmap check. This is such a likely attempt
- * at bad behaviour/exploit that we always want to get the AVC, even
- * if DAC would have also denied the operation.
- */
if (addr < CONFIG_LSM_MMAP_MIN_ADDR) {
+ u32 sid = current_sid();
rc = avc_has_perm(sid, sid, SECCLASS_MEMPROTECT,
MEMPROTECT__MMAP_ZERO, NULL);
- if (rc)
- return rc;
}
- /* do DAC check on address space usage */
- return cap_mmap_addr(addr);
+ return rc;
}
static int selinux_mmap_file(struct file *file, unsigned long reqprot,