95 lines
2.8 KiB
Diff
95 lines
2.8 KiB
Diff
Bugzilla: 1013466
|
|
Upstream-status: 3.15 (commit 98883bfd9d603a2760f6d53eccfaa3ae2c053e72)
|
|
|
|
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>
|
|
---
|
|
security/selinux/hooks.c | 20 ++++++++------------
|
|
1 file changed, 8 insertions(+), 12 deletions(-)
|
|
|
|
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
|
|
index 57b0b49..e3664ae 100644
|
|
--- a/security/selinux/hooks.c
|
|
+++ b/security/selinux/hooks.c
|
|
@@ -3205,24 +3205,20 @@ 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,
|
|
|
|
_______________________________________________
|
|
Selinux mailing list
|
|
Selinux@tycho.nsa.gov
|
|
To unsubscribe, send email to Selinux-leave@tycho.nsa.gov.
|
|
To get help, send an email containing "help" to Selinux-request@tycho.nsa.gov.
|