From: Nikita Zhandarovich n.zhandarovich@fintech.ru

mainline inclusion from mainline-v6.9-rc1 commit 3948abaa4e2be938ccdfc289385a27342fb13d43 category: bugfix bugzilla: 189815 CVE: CVE-2024-26901

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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syzbot identified a kernel information leak vulnerability in do_sys_name_to_handle() and issued the following report [1].

[1] "BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline] BUG: KMSAN: kernel-infoleak in _copy_to_user+0xbc/0x100 lib/usercopy.c:40 instrument_copy_to_user include/linux/instrumented.h:114 [inline] _copy_to_user+0xbc/0x100 lib/usercopy.c:40 copy_to_user include/linux/uaccess.h:191 [inline] do_sys_name_to_handle fs/fhandle.c:73 [inline] __do_sys_name_to_handle_at fs/fhandle.c:112 [inline] __se_sys_name_to_handle_at+0x949/0xb10 fs/fhandle.c:94 __x64_sys_name_to_handle_at+0xe4/0x140 fs/fhandle.c:94 ...

Uninit was created at: slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768 slab_alloc_node mm/slub.c:3478 [inline] __kmem_cache_alloc_node+0x5c9/0x970 mm/slub.c:3517 __do_kmalloc_node mm/slab_common.c:1006 [inline] __kmalloc+0x121/0x3c0 mm/slab_common.c:1020 kmalloc include/linux/slab.h:604 [inline] do_sys_name_to_handle fs/fhandle.c:39 [inline] __do_sys_name_to_handle_at fs/fhandle.c:112 [inline] __se_sys_name_to_handle_at+0x441/0xb10 fs/fhandle.c:94 __x64_sys_name_to_handle_at+0xe4/0x140 fs/fhandle.c:94 ...

Bytes 18-19 of 20 are uninitialized Memory access of size 20 starts at ffff888128a46380 Data copied to user address 0000000020000240"

Per Chuck Lever's suggestion, use kzalloc() instead of kmalloc() to solve the problem.

Fixes: 990d6c2d7aee ("vfs: Add name to file handle conversion support") Suggested-by: Chuck Lever III chuck.lever@oracle.com Reported-and-tested-by: syzbot+09b349b3066c2e0b1e96@syzkaller.appspotmail.com Signed-off-by: Nikita Zhandarovich n.zhandarovich@fintech.ru Link: https://lore.kernel.org/r/20240119153906.4367-1-n.zhandarovich@fintech.ru Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: ZhaoLong Wang wangzhaolong1@huawei.com --- fs/fhandle.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/fhandle.c b/fs/fhandle.c index 718defdf1e0e..744ae0dba99c 100644 --- a/fs/fhandle.c +++ b/fs/fhandle.c @@ -37,7 +37,7 @@ static long do_sys_name_to_handle(struct path *path, if (f_handle.handle_bytes > MAX_HANDLE_SZ) return -EINVAL;

- handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes, + handle = kzalloc(sizeof(struct file_handle) + f_handle.handle_bytes, GFP_KERNEL); if (!handle) return -ENOMEM;