3.16.74-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Christoph Probst kernel@probst.it
commit 6a54b2e002c9d00b398d35724c79f9fe0d9b38fb upstream.
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@probst.it Reviewed-by: Pavel Shilovsky pshilov@microsoft.com Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- fs/cifs/smb2ops.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)
--- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -1000,26 +1000,28 @@ smb21_set_oplock_level(struct cifsInodeI 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); }