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Subject: [PATCH] fs/namespace: fix mntput of ERR_PTR in fsmount error path
Author: kartikey406@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
When vfs_create_mount() fails and returns an error pointer, the
__free(path_put) cleanup attribute causes path_put() to be called
on the error pointer, which then calls mntput() on an invalid
pointer value (e.g., -ENOENT = 0xfffffffffffffff4).
This results in a general protection fault in mntput() when KASAN
tries to check the shadow memory for the near-null address computed
from the error pointer offset.
Fix this by clearing newmount.mnt to NULL after extracting the error
code, preventing the path_put cleanup from operating on the error
pointer.
Reported-by: syzbot+94048264da5715c251f9@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=94048264da5715c251f9
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
fs/namespace.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index e5240df614de..236482fd503f 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4343,8 +4343,11 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
warn_mandlock();
newmount.mnt = vfs_create_mount(fc);
- if (IS_ERR(newmount.mnt))
- return PTR_ERR(newmount.mnt);
+ if (IS_ERR(newmount.mnt)) {
+ ret = PTR_ERR(newmount.mnt);
+ newmount.mnt = NULL;
+ return ret;
+ }
newmount.dentry = dget(fc->root);
newmount.mnt->mnt_flags = mnt_flags;
--
2.43.0