From: Christoph Probst Date: Tue, 7 May 2019 15:16:40 +0000 (+0200) Subject: cifs: fix strcat buffer overflow and reduce raciness in smb21_set_oplock_level() X-Git-Tag: v4.9.179~39 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=5a3e18dce86c18bd90504f362c46d67589c36ac3;p=platform%2Fkernel%2Flinux-amlogic.git cifs: fix strcat buffer overflow and reduce raciness in smb21_set_oplock_level() 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 Reviewed-by: Pavel Shilovsky Signed-off-by: Steve French CC: Stable Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c index 97d8e2a..f7ad2a3 100644 --- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -1413,26 +1413,28 @@ 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); }