From: Jann Horn jannh@google.com
stable inclusion from stable-v6.6.5 commit da2dbbb73e33d8326d7c0bd54810033706d4a3f2 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I8N21P
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 0ac1d13a55eb37d398b63e6ff6db4a09a2c9128c upstream.
kernel_write() requires the caller to ensure that the file is writable. Let's do that directly after looking up the ->send_fd.
We don't need a separate bailout path because the "out" path already does fput() if ->send_filp is non-NULL.
This has no security impact for two reasons:
- the ioctl requires CAP_SYS_ADMIN - __kernel_write() bails out on read-only files - but only since 5.8, see commit a01ac27be472 ("fs: check FMODE_WRITE in __kernel_write")
Reported-and-tested-by: syzbot+12e098239d20385264d3@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=12e098239d20385264d3 Fixes: 31db9f7c23fb ("Btrfs: introduce BTRFS_IOC_SEND for btrfs send/receive") CC: stable@vger.kernel.org # 4.14+ Signed-off-by: Jann Horn jannh@google.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- fs/btrfs/send.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c index 3a566150c531..db94eefda27e 100644 --- a/fs/btrfs/send.c +++ b/fs/btrfs/send.c @@ -8158,7 +8158,7 @@ long btrfs_ioctl_send(struct inode *inode, struct btrfs_ioctl_send_args *arg) }
sctx->send_filp = fget(arg->send_fd); - if (!sctx->send_filp) { + if (!sctx->send_filp || !(sctx->send_filp->f_mode & FMODE_WRITE)) { ret = -EBADF; goto out; }