merged into cifs-2.6.git for-next
On Tue, May 7, 2019 at 10:17 AM Christoph Probst via samba-technical
<samba-technical@xxxxxxxxxxxxxxx> wrote:
>
> Change strcat to strncpy in the "None" case to fix a buffer overflow
> when cinode->oplock is reset to 0 by another thread accessing the same
> cinode. It is never valid to append "None" to any other message.
>
> Consolidate multiple writes to cinode->oplock to reduce raciness.
>
> Signed-off-by: Christoph Probst <kernel@xxxxxxxxx>
> ---
> fs/cifs/smb2ops.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index c36ff0d..aa61dcf 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -2917,26 +2917,28 @@ smb21_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock,
> unsigned int epoch, bool *purge_cache)
> {
> char message[5] = {0};
> + unsigned int new_oplock = 0;
>
> oplock &= 0xFF;
> if (oplock == SMB2_OPLOCK_LEVEL_NOCHANGE)
> return;
>
> - cinode->oplock = 0;
> if (oplock & SMB2_LEASE_READ_CACHING_HE) {
> - cinode->oplock |= CIFS_CACHE_READ_FLG;
> + new_oplock |= CIFS_CACHE_READ_FLG;
> strcat(message, "R");
> }
> if (oplock & SMB2_LEASE_HANDLE_CACHING_HE) {
> - cinode->oplock |= CIFS_CACHE_HANDLE_FLG;
> + new_oplock |= CIFS_CACHE_HANDLE_FLG;
> strcat(message, "H");
> }
> if (oplock & SMB2_LEASE_WRITE_CACHING_HE) {
> - cinode->oplock |= CIFS_CACHE_WRITE_FLG;
> + new_oplock |= CIFS_CACHE_WRITE_FLG;
> strcat(message, "W");
> }
> - if (!cinode->oplock)
> - strcat(message, "None");
> + if (!new_oplock)
> + strncpy(message, "None", sizeof(message));
> +
> + cinode->oplock = new_oplock;
> cifs_dbg(FYI, "%s Lease granted on inode %p\n", message,
> &cinode->vfs_inode);
> }
> --
> 2.1.4
>
>
--
Thanks,
Steve
