vfs: don't allow writes to swap files
Don't let userspace write to an active swap file because the kernel
effectively has a long term lease on the storage and things could get
seriously corrupted if we let this happen.
Change-Id: Ie6beae0d77c4a8af934d27efaef0346a8f98578d
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/mm/mmap.c b/mm/mmap.c
index fa92452..eae945d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1498,8 +1498,12 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
switch (flags & MAP_TYPE) {
case MAP_SHARED:
- if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
- return -EACCES;
+ if (prot & PROT_WRITE) {
+ if (!(file->f_mode & FMODE_WRITE))
+ return -EACCES;
+ if (IS_SWAPFILE(file->f_mapping->host))
+ return -ETXTBSY;
+ }
/*
* Make sure we don't allow writing to an append-only