cifs: Limit memory used by lock request calls to a page

The code tries to allocate a contiguous buffer with a size supplied by
the server (maxBuf). This could fail if memory is fragmented since it
results in high order allocations for commonly used server
implementations. It is also wasteful since there are probably
few locks in the usual case. Limit the buffer to be no larger than a
page to avoid memory allocation failures due to fragmentation.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index e3e3a75..673f948 100644 (file)
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1140,6 +1140,10 @@ cifs_push_mandatory_locks(struct cifsFileInfo *cfile)
                return -EINVAL;
        }
 
+       BUILD_BUG_ON(sizeof(struct smb_hdr) + sizeof(LOCKING_ANDX_RANGE) >
+                    PAGE_SIZE);
+       max_buf = min_t(unsigned int, max_buf - sizeof(struct smb_hdr),
+                       PAGE_SIZE);
        max_num = (max_buf - sizeof(struct smb_hdr)) /
                                                sizeof(LOCKING_ANDX_RANGE);
        buf = kcalloc(max_num, sizeof(LOCKING_ANDX_RANGE), GFP_KERNEL);
@@ -1478,6 +1482,10 @@ cifs_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock,
        if (!max_buf)
                return -EINVAL;
 
+       BUILD_BUG_ON(sizeof(struct smb_hdr) + sizeof(LOCKING_ANDX_RANGE) >
+                    PAGE_SIZE);
+       max_buf = min_t(unsigned int, max_buf - sizeof(struct smb_hdr),
+                       PAGE_SIZE);
        max_num = (max_buf - sizeof(struct smb_hdr)) /
                                                sizeof(LOCKING_ANDX_RANGE);
        buf = kcalloc(max_num, sizeof(LOCKING_ANDX_RANGE), GFP_KERNEL);

diff --git a/fs/cifs/smb2file.c b/fs/cifs/smb2file.c
index 4ed10dd..eff01ed 100644 (file)
--- a/fs/cifs/smb2file.c
+++ b/fs/cifs/smb2file.c
@@ -128,6 +128,8 @@ smb2_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock,
        if (!max_buf)
                return -EINVAL;
 
+       BUILD_BUG_ON(sizeof(struct smb2_lock_element) > PAGE_SIZE);
+       max_buf = min_t(unsigned int, max_buf, PAGE_SIZE);
        max_num = max_buf / sizeof(struct smb2_lock_element);
        buf = kcalloc(max_num, sizeof(struct smb2_lock_element), GFP_KERNEL);
        if (!buf)
@@ -264,6 +266,8 @@ smb2_push_mandatory_locks(struct cifsFileInfo *cfile)
                return -EINVAL;
        }
 
+       BUILD_BUG_ON(sizeof(struct smb2_lock_element) > PAGE_SIZE);
+       max_buf = min_t(unsigned int, max_buf, PAGE_SIZE);
        max_num = max_buf / sizeof(struct smb2_lock_element);
        buf = kcalloc(max_num, sizeof(struct smb2_lock_element), GFP_KERNEL);
        if (!buf) {