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Fix MAC-before-DAC check for mmap_zero (rhbz 1013466)

This commit is contained in:
Josh Boyer 2014-03-04 14:05:27 -05:00
parent 49ba872419
commit 84df599928
2 changed files with 101 additions and 0 deletions
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7
kernel.spec
View File

@ -791,6 +791,9 @@ Patch25031: net-fix-for-a-race-condition-in-the-inet-frag-code.patch
#rhbz 1027465
Patch25032: HID-Bluetooth-hidp-make-sure-input-buffers-are-big-e.patch
#rhbz 1013466
Patch25033: selinux-put-the-mmap-DAC-controls-before-the-MAC-controls.patch
# END OF PATCH DEFINITIONS
%endif
@ -1528,6 +1531,9 @@ ApplyPatch net-fix-for-a-race-condition-in-the-inet-frag-code.patch
#rhbz 1027465
ApplyPatch HID-Bluetooth-hidp-make-sure-input-buffers-are-big-e.patch
#rhbz 1013466
ApplyPatch selinux-put-the-mmap-DAC-controls-before-the-MAC-controls.patch
# END OF PATCH APPLICATIONS
%endif
@ -2341,6 +2347,7 @@ fi
%changelog
* Tue Mar 04 2014 Josh Boyer <jwboyer@fedoraproject.org>
- Fix MAC-before-DAC check for mmap_zero (rhbz 1013466)
- Fix hidp crash with apple bluetooth trackpads (rhbz 1027465)
* Mon Mar 03 2014 Josh Boyer <jwboyer@fedoraproject.org> - 3.13.5-103

94
selinux-put-the-mmap-DAC-controls-before-the-MAC-controls.patch Normal file
View File

@ -0,0 +1,94 @@
Bugzilla: 1013466
Upstream-status: queued for 3.14/3.15? http://marc.info/?l=selinux&m=139351174702148&w=2
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,
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