From d11c3f780c87198ac9d94f954e66d651677b532a Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Mon, 7 Nov 2022 16:50:00 +0000 Subject: [PATCH] UPSTREAM: mm/damon/dbgfs: check if rm_contexts input is for a real context 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/000000000000ede3ac05ec4abf8e@google.com/ Bug: 254441685 Link: https://lkml.kernel.org/r/20221107165001.5717-2-sj@kernel.org Fixes: 75c1c2b53c78 ("mm/damon/dbgfs: support multiple contexts") Signed-off-by: SeongJae Park Reported-by: syzbot+6087eafb76a94c4ac9eb@syzkaller.appspotmail.com Cc: [5.15.x] Signed-off-by: Andrew Morton (cherry picked from commit 1de09a7281edecfdba19b3a07417f6d65243ab5f) Signed-off-by: Lee Jones Change-Id: I038612db15c0a46089a5e1a52a4750fff6ba3bf6 --- mm/damon/dbgfs.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c index f2772fc740c0..819c337c22ff 100644 --- a/mm/damon/dbgfs.c +++ b/mm/damon/dbgfs.c @@ -785,6 +785,7 @@ 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; @@ -800,6 +801,12 @@ 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) {