Changes from v1
(https://lore.kernel.org/damon/[email protected]/)
- Rebase on latest mm-unstable
---
This patchset is for fixing (patch 1) the syzbot-reported
slab-out-of-bounds write in dbgfs_rm_context_write[1], and adding a
selftest for the bug (patch 2).
[1] https://lore.kernel.org/damon/[email protected]/
SeongJae Park (2):
mm/damon/dbgfs: check if rm_contexts input is for a real context
selftests/damon: test non-context inputs to rm_contexts file
mm/damon/dbgfs.c | 7 +++++++
tools/testing/selftests/damon/Makefile | 1 +
.../damon/debugfs_rm_non_contexts.sh | 19 +++++++++++++++++++
3 files changed, 27 insertions(+)
create mode 100755 tools/testing/selftests/damon/debugfs_rm_non_contexts.sh
--
2.25.1
A user could write a name of a file under 'damon/' debugfs directory,
which is not a user-created context, to 'rm_contexts' file. In the
case, 'dbgfs_rm_context()' just assumes it's the valid DAMON context
directory only if a file of the name exist. As a result, invalid memory
access could happen as below. Fix the bug by checking if the given
input is for a directory. This check can filter out non-context inputs
because directories under 'damon/' debugfs directory can be created via
only 'mk_contexts' file.
This bug has found by syzbot[1].
[1] https://lore.kernel.org/damon/[email protected]/
Reported-by: [email protected]
Fixes: 75c1c2b53c78 ("mm/damon/dbgfs: support multiple contexts")
Cc: <[email protected]> # 5.15.x
Signed-off-by: SeongJae Park <[email protected]>
---
mm/damon/dbgfs.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index 6f0ae7d3ae39..b3f454a5c682 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -890,6 +890,7 @@ static ssize_t dbgfs_mk_context_write(struct file *file,
static int dbgfs_rm_context(char *name)
{
struct dentry *root, *dir, **new_dirs;
+ struct inode *inode;
struct damon_ctx **new_ctxs;
int i, j;
int ret = 0;
@@ -905,6 +906,12 @@ static int dbgfs_rm_context(char *name)
if (!dir)
return -ENOENT;
+ inode = d_inode(dir);
+ if (!S_ISDIR(inode->i_mode)) {
+ ret = -EINVAL;
+ goto out_dput;
+ }
+
new_dirs = kmalloc_array(dbgfs_nr_ctxs - 1, sizeof(*dbgfs_dirs),
GFP_KERNEL);
if (!new_dirs) {
--
2.25.1
There was a bug[1] that triggered by writing non-context DAMON debugfs
file names to the 'rm_contexts' DAMON debugfs file. Add a selftest for
the bug to avoid it happen again.
[1] https://lore.kernel.org/damon/[email protected]/
Signed-off-by: SeongJae Park <[email protected]>
---
tools/testing/selftests/damon/Makefile | 1 +
.../damon/debugfs_rm_non_contexts.sh | 19 +++++++++++++++++++
2 files changed, 20 insertions(+)
create mode 100755 tools/testing/selftests/damon/debugfs_rm_non_contexts.sh
diff --git a/tools/testing/selftests/damon/Makefile b/tools/testing/selftests/damon/Makefile
index af490acc5348..838a8e49f77b 100644
--- a/tools/testing/selftests/damon/Makefile
+++ b/tools/testing/selftests/damon/Makefile
@@ -7,6 +7,7 @@ TEST_FILES = _chk_dependency.sh _debugfs_common.sh
TEST_PROGS = debugfs_attrs.sh debugfs_schemes.sh debugfs_target_ids.sh
TEST_PROGS += debugfs_empty_targets.sh debugfs_huge_count_read_write.sh
TEST_PROGS += debugfs_duplicate_context_creation.sh
+TEST_PROGS += debugfs_rm_non_contexts.sh
TEST_PROGS += sysfs.sh
TEST_PROGS += reclaim.sh lru_sort.sh
diff --git a/tools/testing/selftests/damon/debugfs_rm_non_contexts.sh b/tools/testing/selftests/damon/debugfs_rm_non_contexts.sh
new file mode 100755
index 000000000000..48b7af6b022c
--- /dev/null
+++ b/tools/testing/selftests/damon/debugfs_rm_non_contexts.sh
@@ -0,0 +1,19 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+source _debugfs_common.sh
+
+# Test putting non-ctx files/dirs to rm_contexts file
+# ===================================================
+
+dmesg -C
+
+for file in "$DBGFS/"*
+do
+ echo "$(basename "$f")" > "$DBGFS/rm_contexts"
+ if dmesg | grep -q BUG
+ then
+ dmesg
+ exit 1
+ fi
+done
--
2.25.1