process_madvise() used to validate the advice while walking each
imported iovec. If the vector has zero total length, vector_madvise()
does not enter the loop and can return success without checking whether
the advice value is valid.
For a local mm, such as process_madvise(PIDFD_SELF, ...), the remote-only
process_madvise_remote_valid() check is skipped. As a result, an invalid
advice can be reported as success when the vector has zero total length.
This differs from madvise(), which rejects an invalid advice before
returning success for a zero-length range.
Validate the generic madvise behavior at the syscall-facing entry points
before any vector walk. In process_madvise(), do this before the
remote-only advice restriction so unsupported advice is rejected with the
same priority for local and remote mm.
Use an errno-returning helper for address/length validation, and handle
zero-length ranges explicitly at the call sites. Requests with valid
advice and zero total length remain a noop and continue to return 0. Add
a selftest that covers invalid advice with a zero-length iovec and an
empty vector, while also checking that a request with valid advice and
zero length still succeeds.
Fixes: 021781b01275 ("mm/madvise: unrestrict process_madvise() for current
process")
Acked-by: David Hildenbrand (Arm) <[email protected]>
Reviewed-by: SeongJae Park <[email protected]>
Signed-off-by: fujunjie <[email protected]>
---
v3:
- Rework range validation into check_input_range() and handle zero-length
ranges explicitly at the call sites, per Lorenzo.
- Drop the unnecessary errno reset in the selftest, per SJ.
Testing: built mm/madvise.o, bzImage and process_madv; process_madv
passes 7/7 in QEMU.
mm/madvise.c | 60 +++++++++++++------------------
tools/testing/selftests/mm/process_madv.c | 28 ++++++++++++++++
2 files changed, 53 insertions(+), 35 deletions(-)
diff --git a/mm/madvise.c b/mm/madvise.c
index 69708e953cf56..cd9bb077072c 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1834,50 +1834,29 @@ static void madvise_finish_tlb(struct madvise_behavior
*madv_behavior)
tlb_finish_mmu(madv_behavior->tlb);
}
-static bool is_valid_madvise(unsigned long start, size_t len_in, int behavior)
+/**
+ * check_input_range() - Check if the requested range is valid.
+ * @start: Start address of madvise-requested address range.
+ * @len_in: Length of madvise-requested address range.
+ *
+ * Returns: 0 if the input range is valid, otherwise an error code.
+ */
+static int check_input_range(unsigned long start, size_t len_in)
{
size_t len;
- if (!madvise_behavior_valid(behavior))
- return false;
-
if (!PAGE_ALIGNED(start))
- return false;
+ return -EINVAL;
len = PAGE_ALIGN(len_in);
/* Check to see whether len was rounded up from small -ve to zero */
if (len_in && !len)
- return false;
+ return -EINVAL;
if (start + len < start)
- return false;
-
- return true;
-}
+ return -EINVAL;
-/*
- * madvise_should_skip() - Return if the request is invalid or nothing.
- * @start: Start address of madvise-requested address range.
- * @len_in: Length of madvise-requested address range.
- * @behavior: Requested madvise behavior.
- * @err: Pointer to store an error code from the check.
- *
- * If the specified behaviour is invalid or nothing would occur, we skip the
- * operation. This function returns true in the cases, otherwise false. In
- * the former case we store an error on @err.
- */
-static bool madvise_should_skip(unsigned long start, size_t len_in,
- int behavior, int *err)
-{
- if (!is_valid_madvise(start, len_in, behavior)) {
- *err = -EINVAL;
- return true;
- }
- if (start + PAGE_ALIGN(len_in) == start) {
- *err = 0;
- return true;
- }
- return false;
+ return 0;
}
static bool is_madvise_populate(struct madvise_behavior *madv_behavior)
@@ -2013,8 +1992,13 @@ int do_madvise(struct mm_struct *mm, unsigned long
start, size_t len_in, int beh
.tlb = &tlb,
};
- if (madvise_should_skip(start, len_in, behavior, &error))
+ if (!madvise_behavior_valid(behavior))
+ return -EINVAL;
+
+ error = check_input_range(start, len_in);
+ if (error || !len_in)
return error;
+
error = madvise_lock(&madv_behavior);
if (error)
return error;
@@ -2056,7 +2040,8 @@ static ssize_t vector_madvise(struct mm_struct *mm,
struct iov_iter *iter,
size_t len_in = iter_iov_len(iter);
int error;
- if (madvise_should_skip(start, len_in, behavior, &error))
+ error = check_input_range(start, len_in);
+ if (error || !len_in)
ret = error;
else
ret = madvise_do_behavior(start, len_in,
&madv_behavior);
@@ -2131,6 +2116,11 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const
struct iovec __user *, vec,
goto release_task;
}
+ if (!madvise_behavior_valid(behavior)) {
+ ret = -EINVAL;
+ goto release_mm;
+ }
+
/*
* We need only perform this check if we are attempting to manipulate a
* remote process's address space.
diff --git a/tools/testing/selftests/mm/process_madv.c
b/tools/testing/selftests/mm/process_madv.c
index cd4610baf5d7d..3fffd5f7e6fb4 100644
--- a/tools/testing/selftests/mm/process_madv.c
+++ b/tools/testing/selftests/mm/process_madv.c
@@ -309,6 +309,34 @@ TEST_F(process_madvise, invalid_vlen)
ASSERT_EQ(munmap(map, pagesize), 0);
}
+/*
+ * Test that invalid advice is rejected even when the iovec has zero total
+ * length. A request with valid advice and zero length is a noop, but
+ * invalid advice should still fail with EINVAL.
+ */
+TEST_F(process_madvise, invalid_advice_zero_length)
+{
+ struct iovec vec = {
+ .iov_base = NULL,
+ .iov_len = 0,
+ };
+ int pidfd = self->pidfd;
+ ssize_t ret;
+
+ errno = 0;
+ ret = sys_process_madvise(pidfd, &vec, 1, -1, 0);
+ ASSERT_EQ(ret, -1);
+ ASSERT_EQ(errno, EINVAL);
+
+ errno = 0;
+ ret = sys_process_madvise(pidfd, &vec, 1, MADV_DONTNEED, 0);
+ ASSERT_EQ(ret, 0);
+
+ ret = sys_process_madvise(pidfd, NULL, 0, -1, 0);
+ ASSERT_EQ(ret, -1);
+ ASSERT_EQ(errno, EINVAL);
+}
+
/*
* Test process_madvise() with an invalid flag value. Currently, only a flag
* value of 0 is supported. This test is reserved for the future, e.g., if
base-commit: 1b55f8358e35a67bf3969339ea7b86988af92f66
--
2.34.1
