Message ID | 20211115035721.1909-2-thunder.leizhen@huawei.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | pipe: Fix a potential UAF and delete a duplicate line of code | expand |
On Mon, Nov 15, 2021 at 11:57:20AM +0800, Zhen Lei wrote: > if (!buf->len) { > + unsigned int __maybe_unused flags = buf->flags; Why __maybe_unused?
On 2021/11/15 12:25, Matthew Wilcox wrote: > On Mon, Nov 15, 2021 at 11:57:20AM +0800, Zhen Lei wrote: >> if (!buf->len) { >> + unsigned int __maybe_unused flags = buf->flags; > > Why __maybe_unused? It's used only if "#ifdef CONFIG_WATCH_QUEUE". Otherwise, a warning will be reported. > . >
On Mon, Nov 15, 2021 at 02:13:44PM +0800, Leizhen (ThunderTown) wrote: > > > On 2021/11/15 12:25, Matthew Wilcox wrote: > > On Mon, Nov 15, 2021 at 11:57:20AM +0800, Zhen Lei wrote: > >> if (!buf->len) { > >> + unsigned int __maybe_unused flags = buf->flags; > > > > Why __maybe_unused? > > It's used only if "#ifdef CONFIG_WATCH_QUEUE". Otherwise, a warning will be reported. Better to turn the #ifdef into if (IS_ENABLED())
On 2021/11/15 21:05, Matthew Wilcox wrote: > On Mon, Nov 15, 2021 at 02:13:44PM +0800, Leizhen (ThunderTown) wrote: >> >> >> On 2021/11/15 12:25, Matthew Wilcox wrote: >>> On Mon, Nov 15, 2021 at 11:57:20AM +0800, Zhen Lei wrote: >>>> if (!buf->len) { >>>> + unsigned int __maybe_unused flags = buf->flags; >>> >>> Why __maybe_unused? >> >> It's used only if "#ifdef CONFIG_WATCH_QUEUE". Otherwise, a warning will be reported. > > Better to turn the #ifdef into if (IS_ENABLED()) Hi, Matthew: Thank you for your advice. IS_ENABLED() is a good idea, but when I tried it, I found that the macro 'PIPE_BUF_FLAG_LOSS' and the structure member 'note_loss' were also separated by "ifdef CONFIG_WATCH_QUEUE", so this method is not suitable here. #ifdef CONFIG_WATCH_QUEUE #define PIPE_BUF_FLAG_LOSS 0x40 /* Message loss happened after this buffer */ #endif @@ -62,9 +60,7 @@ struct pipe_inode_info { unsigned int tail; unsigned int max_usage; unsigned int ring_size; #ifdef CONFIG_WATCH_QUEUE bool note_loss; #endif > . >
diff --git a/fs/pipe.c b/fs/pipe.c index 6d4342bad9f15b2..302f1e50ce3be1d 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -319,10 +319,12 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) } if (!buf->len) { + unsigned int __maybe_unused flags = buf->flags; + pipe_buf_release(pipe, buf); spin_lock_irq(&pipe->rd_wait.lock); #ifdef CONFIG_WATCH_QUEUE - if (buf->flags & PIPE_BUF_FLAG_LOSS) + if (flags & PIPE_BUF_FLAG_LOSS) pipe->note_loss = true; #endif tail++;
Accessing buf->flags after pipe_buf_release(pipe, buf) is unsafe, because the 'buf' memory maybe freed. Fixes: e7d553d69cf6 ("pipe: Add notification lossage handling") Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> --- fs/pipe.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)