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-rw-r--r--kernel/file.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/file.c b/kernel/file.c
index fc87c09..116eb97 100644
--- a/kernel/file.c
+++ b/kernel/file.c
@@ -114,6 +114,8 @@ fileread(struct file *f, uint64 addr, int n)
if(f->type == FD_PIPE){
r = piperead(f->pipe, addr, n);
} else if(f->type == FD_DEVICE){
+ if(f->major < 0 || f->major >= NDEV || !devsw[f->major].read)
+ return -1;
r = devsw[f->major].read(1, addr, n);
} else if(f->type == FD_INODE){
ilock(f->ip);
@@ -140,6 +142,8 @@ filewrite(struct file *f, uint64 addr, int n)
if(f->type == FD_PIPE){
ret = pipewrite(f->pipe, addr, n);
} else if(f->type == FD_DEVICE){
+ if(f->major < 0 || f->major >= NDEV || !devsw[f->major].write)
+ return -1;
ret = devsw[f->major].write(1, addr, n);
} else if(f->type == FD_INODE){
// write a few blocks at a time to avoid exceeding