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cifs: fix strcat buffer overflow and reduce raciness in smb21_set_oplock_level() 

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>
This commit is contained in:
Christoph Probst 2019-05-07 17:16:40 +02:00 committed by Steve French
parent 26ea888f62
commit 6a54b2e002
1 changed files with 8 additions and 6 deletions
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14
fs/cifs/smb2ops.c
View File

@ -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);
}