This is a note to let you know that I've just added the patch titled
btrfs: send: ensure send_fd is writable
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
btrfs-send-ensure-send_fd-is-writable.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0ac1d13a55eb37d398b63e6ff6db4a09a2c9128c Mon Sep 17 00:00:00 2001
From: Jann Horn <jannh@xxxxxxxxxx>
Date: Fri, 24 Nov 2023 17:48:31 +0100
Subject: btrfs: send: ensure send_fd is writable
From: Jann Horn <jannh@xxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=12e098239d20385264d3
Fixes: 31db9f7c23fb ("Btrfs: introduce BTRFS_IOC_SEND for btrfs send/receive")
CC: stable@xxxxxxxxxxxxxxx # 4.14+
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/send.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -6860,7 +6860,7 @@ long btrfs_ioctl_send(struct file *mnt_f
sctx->flags = arg->flags;
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;
}
Patches currently in stable-queue which might be from jannh@xxxxxxxxxx are
queue-4.19/btrfs-send-ensure-send_fd-is-writable.patch
