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| author | Jann Horn <jannh@google.com> | 2023-11-24 17:48:31 +0100 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2023-11-24 18:50:53 +0100 |
| commit | 0ac1d13a55eb37d398b63e6ff6db4a09a2c9128c (patch) | |
| tree | fba242da216d9858ef320067bdc71c57c67e3fac /fs/btrfs/send.c | |
| parent | 94dbf7c0871f7ae6349ba4b0341ce8f5f98a071d (diff) | |
| download | lwn-0ac1d13a55eb37d398b63e6ff6db4a09a2c9128c.tar.gz lwn-0ac1d13a55eb37d398b63e6ff6db4a09a2c9128c.zip | |
btrfs: send: ensure send_fd is writable
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>
Diffstat (limited to 'fs/btrfs/send.c')
| -rw-r--r-- | fs/btrfs/send.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c index 3b929f0e8f04..4e36550618e5 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; } |