Commit 6a54b2e0 authored by Christoph Probst's avatar Christoph Probst Committed by Steve French

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: default avatarChristoph Probst <kernel@probst.it>
Reviewed-by: default avatarPavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
CC: Stable <stable@vger.kernel.org>
parent 26ea888f
...@@ -2974,26 +2974,28 @@ smb21_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock, ...@@ -2974,26 +2974,28 @@ smb21_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock,
unsigned int epoch, bool *purge_cache) unsigned int epoch, bool *purge_cache)
{ {
char message[5] = {0}; char message[5] = {0};
unsigned int new_oplock = 0;
oplock &= 0xFF; oplock &= 0xFF;
if (oplock == SMB2_OPLOCK_LEVEL_NOCHANGE) if (oplock == SMB2_OPLOCK_LEVEL_NOCHANGE)
return; return;
cinode->oplock = 0;
if (oplock & SMB2_LEASE_READ_CACHING_HE) { if (oplock & SMB2_LEASE_READ_CACHING_HE) {
cinode->oplock |= CIFS_CACHE_READ_FLG; new_oplock |= CIFS_CACHE_READ_FLG;
strcat(message, "R"); strcat(message, "R");
} }
if (oplock & SMB2_LEASE_HANDLE_CACHING_HE) { if (oplock & SMB2_LEASE_HANDLE_CACHING_HE) {
cinode->oplock |= CIFS_CACHE_HANDLE_FLG; new_oplock |= CIFS_CACHE_HANDLE_FLG;
strcat(message, "H"); strcat(message, "H");
} }
if (oplock & SMB2_LEASE_WRITE_CACHING_HE) { if (oplock & SMB2_LEASE_WRITE_CACHING_HE) {
cinode->oplock |= CIFS_CACHE_WRITE_FLG; new_oplock |= CIFS_CACHE_WRITE_FLG;
strcat(message, "W"); strcat(message, "W");
} }
if (!cinode->oplock) if (!new_oplock)
strcat(message, "None"); strncpy(message, "None", sizeof(message));
cinode->oplock = new_oplock;
cifs_dbg(FYI, "%s Lease granted on inode %p\n", message, cifs_dbg(FYI, "%s Lease granted on inode %p\n", message,
&cinode->vfs_inode); &cinode->vfs_inode);
} }
......
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