path: root/security
diff options
authorPaul Moore <pmoore@redhat.com>2014-03-19 16:46:11 -0400
committerPaul Moore <pmoore@redhat.com>2014-03-19 16:46:11 -0400
commit98883bfd9d603a2760f6d53eccfaa3ae2c053e72 (patch)
tree48454c4cd6d2c490796be28f0376d4f21dad227c /security
parentselinux: fix the output of ./scripts/get_maintainer.pl for SELinux (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>
Diffstat (limited to 'security')
1 files changed, 8 insertions, 12 deletions
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 0e68bdbe020a..1dd948485e48 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3188,24 +3188,20 @@ 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.
- */
+ u32 sid = current_sid();
rc = avc_has_perm(sid, sid, SECCLASS_MEMPROTECT,
- 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,