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authorKP Singh <kpsingh@google.com>2020-04-02 22:07:51 +0200
committerAlexei Starovoitov <ast@kernel.org>2020-04-02 19:42:52 -0700
commit5222d69642a09261222fb9703761a029db16cadf (patch)
tree79a2b386c0cc2f1dbbcd1e186f5b38ecb6947447
parent7a1ca97269ee197ea967de2c9412d8e7e2274ee6 (diff)
bpf, lsm: Fix the file_mprotect LSM test.
The test was previously using an mprotect on the heap memory allocated using malloc and was expecting the allocation to be always using sbrk(2). This is, however, not always true and in certain conditions malloc may end up using anonymous mmaps for heap alloctions. This means that the following condition that is used in the "lsm/file_mprotect" program is not sufficent to detect all mprotect calls done on heap memory: is_heap = (vma->vm_start >= vma->vm_mm->start_brk && vma->vm_end <= vma->vm_mm->brk); The test is updated to use an mprotect on memory allocated on the stack. While this would result in the splitting of the vma, this happens only after the security_file_mprotect hook. So, the condition used in the BPF program holds true. Fixes: 03e54f100d57 ("bpf: lsm: Add selftests for BPF_PROG_TYPE_LSM") Reported-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: KP Singh <kpsingh@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200402200751.26372-1-kpsingh@chromium.org
-rw-r--r--tools/testing/selftests/bpf/prog_tests/test_lsm.c18
-rw-r--r--tools/testing/selftests/bpf/progs/lsm.c8
2 files changed, 13 insertions, 13 deletions
diff --git a/tools/testing/selftests/bpf/prog_tests/test_lsm.c b/tools/testing/selftests/bpf/prog_tests/test_lsm.c
index 1e4c258de09d..b17eb2045c1d 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_lsm.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_lsm.c
@@ -15,7 +15,10 @@
char *CMD_ARGS[] = {"true", NULL};
-int heap_mprotect(void)
+#define GET_PAGE_ADDR(ADDR, PAGE_SIZE) \
+ (char *)(((unsigned long) (ADDR + PAGE_SIZE)) & ~(PAGE_SIZE-1))
+
+int stack_mprotect(void)
{
void *buf;
long sz;
@@ -25,12 +28,9 @@ int heap_mprotect(void)
if (sz < 0)
return sz;
- buf = memalign(sz, 2 * sz);
- if (buf == NULL)
- return -ENOMEM;
-
- ret = mprotect(buf, sz, PROT_READ | PROT_WRITE | PROT_EXEC);
- free(buf);
+ buf = alloca(sz * 3);
+ ret = mprotect(GET_PAGE_ADDR(buf, sz), sz,
+ PROT_READ | PROT_WRITE | PROT_EXEC);
return ret;
}
@@ -73,8 +73,8 @@ void test_test_lsm(void)
skel->bss->monitored_pid = getpid();
- err = heap_mprotect();
- if (CHECK(errno != EPERM, "heap_mprotect", "want errno=EPERM, got %d\n",
+ err = stack_mprotect();
+ if (CHECK(errno != EPERM, "stack_mprotect", "want err=EPERM, got %d\n",
errno))
goto close_prog;
diff --git a/tools/testing/selftests/bpf/progs/lsm.c b/tools/testing/selftests/bpf/progs/lsm.c
index a4e3c223028d..b4598d4bc4f7 100644
--- a/tools/testing/selftests/bpf/progs/lsm.c
+++ b/tools/testing/selftests/bpf/progs/lsm.c
@@ -23,12 +23,12 @@ int BPF_PROG(test_int_hook, struct vm_area_struct *vma,
return ret;
__u32 pid = bpf_get_current_pid_tgid() >> 32;
- int is_heap = 0;
+ int is_stack = 0;
- is_heap = (vma->vm_start >= vma->vm_mm->start_brk &&
- vma->vm_end <= vma->vm_mm->brk);
+ is_stack = (vma->vm_start <= vma->vm_mm->start_stack &&
+ vma->vm_end >= vma->vm_mm->start_stack);
- if (is_heap && monitored_pid == pid) {
+ if (is_stack && monitored_pid == pid) {
mprotect_count++;
ret = -EPERM;
}