From 7acbaa16b99edaf8ef432229d4b7a6f3b666767d Mon Sep 17 00:00:00 2001 From: Huiwen He Date: Mon, 8 Jun 2026 23:57:29 +0800 Subject: [PATCH] smb/client: always return a value for FS_IOC_GETFLAGS Currently, repeated lsattr calls on a regular CIFS file without the compressed attribute may show random flags: $ touch test.bin $ lsattr test.bin s-S-ia-A-EjI---------m test.bin $ lsattr test.bin ------d-cEjI---------m test.bin The lsattr reproducer depends on the previous contents of its userspace buffer, so it may not reproduce on every setup. A deterministic reproducer is to initialize the ioctl argument before FS_IOC_GETFLAGS on a file without the compressed attribute: int flags = 0x7fffffff; ioctl(fd, FS_IOC_GETFLAGS, &flags); On an affected kernel, flags remains 0x7fffffff. With the fix, it is set to 0. This happens because when the cached inode does not have the compressed bit set, the CIFS fallback path in FS_IOC_GETFLAGS returns success without calling put_user() to write the zero flags value into the user buffer. As a result, the caller observes stale contents from its own buffer. Fix this by always writing the visible flags value back to the user buffer before returning success, even when the value is zero. Fixes: 64a5cfa6db94 ("Allow setting per-file compression via SMB2/3") Signed-off-by: Huiwen He Reviewed-by: ChenXiaoSong Signed-off-by: Steve French --- fs/smb/client/ioctl.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/fs/smb/client/ioctl.c b/fs/smb/client/ioctl.c index 17408bb8ab65..746d70091f3d 100644 --- a/fs/smb/client/ioctl.c +++ b/fs/smb/client/ioctl.c @@ -392,13 +392,11 @@ long cifs_ioctl(struct file *filep, unsigned int command, unsigned long arg) } #endif /* CONFIG_CIFS_ALLOW_INSECURE_LEGACY */ #endif /* CONFIG_CIFS_POSIX */ - rc = 0; - if (CIFS_I(inode)->cifsAttrs & ATTR_COMPRESSED) { - /* add in the compressed bit */ - ExtAttrBits = FS_COMPR_FL; - rc = put_user(ExtAttrBits & FS_FL_USER_VISIBLE, - (int __user *)arg); - } + if (CIFS_I(inode)->cifsAttrs & FILE_ATTRIBUTE_COMPRESSED) + ExtAttrBits |= FS_COMPR_FL; + + rc = put_user(ExtAttrBits & FS_FL_USER_VISIBLE, + (int __user *)arg); break; case FS_IOC_SETFLAGS: if (pSMBFile == NULL)