lkml.org 
[lkml]   [2019]   [May]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2] cifs: fix strcat buffer overflow and reduce raciness in smb21_set_oplock_level()
Date
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>
---
fs/cifs/smb2ops.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index c36ff0d..aa61dcf 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -2917,26 +2917,28 @@ 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);
}
--
2.1.4
\
 
 \ /
  Last update: 2019-05-07 17:17    [W:0.051 / U:0.296 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site