cifs: fix strcat buffer overflow and reduce raciness in smb21_set_oplock_level() (6a54b2e0) · Commits · 戴 / test

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> CC: Stable <stable@vger.kernel.org>

fs/cifs/smb2ops.c

+8 −6

Original line number	Diff line number	Diff line
		@@ -2974,26 +2974,28 @@ 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);
		}

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