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authorJann Horn <jannh@google.com>2019-01-23 15:19:17 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-03-23 13:19:47 +0100
commit943ebf4d8c50dcbd474483b023955f4716e0c5bb (patch)
tree58a8e8c9e0eaa4f78bc8bb9e72455d734be9701c
parent8c93709f25e738b6cfea72eda0a0593365f049ea (diff)
splice: don't merge into linked buffers
commit a0ce2f0aa6ad97c3d4927bf2ca54bcebdf062d55 upstream. Before this patch, it was possible for two pipes to affect each other after data had been transferred between them with tee(): ============ $ cat tee_test.c int main(void) { int pipe_a[2]; if (pipe(pipe_a)) err(1, "pipe"); int pipe_b[2]; if (pipe(pipe_b)) err(1, "pipe"); if (write(pipe_a[1], "abcd", 4) != 4) err(1, "write"); if (tee(pipe_a[0], pipe_b[1], 2, 0) != 2) err(1, "tee"); if (write(pipe_b[1], "xx", 2) != 2) err(1, "write"); char buf[5]; if (read(pipe_a[0], buf, 4) != 4) err(1, "read"); buf[4] = 0; printf("got back: '%s'\n", buf); } $ gcc -o tee_test tee_test.c $ ./tee_test got back: 'abxx' $ ============ As suggested by Al Viro, fix it by creating a separate type for non-mergeable pipe buffers, then changing the types of buffers in splice_pipe_to_pipe() and link_pipe(). Cc: <stable@vger.kernel.org> Fixes: 7c77f0b3f920 ("splice: implement pipe to pipe splicing") Fixes: 70524490ee2e ("[PATCH] splice: add support for sys_tee()") Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/pipe.c14
-rw-r--r--fs/splice.c4
-rw-r--r--include/linux/pipe_fs_i.h1
3 files changed, 19 insertions, 0 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
index 34345535f63d..388e09a689de 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -238,6 +238,14 @@ static const struct pipe_buf_operations anon_pipe_buf_ops = {
.get = generic_pipe_buf_get,
};
+static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {
+ .can_merge = 0,
+ .confirm = generic_pipe_buf_confirm,
+ .release = anon_pipe_buf_release,
+ .steal = anon_pipe_buf_steal,
+ .get = generic_pipe_buf_get,
+};
+
static const struct pipe_buf_operations packet_pipe_buf_ops = {
.can_merge = 0,
.confirm = generic_pipe_buf_confirm,
@@ -246,6 +254,12 @@ static const struct pipe_buf_operations packet_pipe_buf_ops = {
.get = generic_pipe_buf_get,
};
+void pipe_buf_mark_unmergeable(struct pipe_buffer *buf)
+{
+ if (buf->ops == &anon_pipe_buf_ops)
+ buf->ops = &anon_pipe_buf_nomerge_ops;
+}
+
static ssize_t
pipe_read(struct kiocb *iocb, struct iov_iter *to)
{
diff --git a/fs/splice.c b/fs/splice.c
index 8dd79ecfd383..01983bea760c 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1594,6 +1594,8 @@ retry:
*/
obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
+ pipe_buf_mark_unmergeable(obuf);
+
obuf->len = len;
opipe->nrbufs++;
ibuf->offset += obuf->len;
@@ -1668,6 +1670,8 @@ static int link_pipe(struct pipe_inode_info *ipipe,
*/
obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
+ pipe_buf_mark_unmergeable(obuf);
+
if (obuf->len > len)
obuf->len = len;
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index e7497c9dde7f..4f7129389855 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -182,6 +182,7 @@ void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
+void pipe_buf_mark_unmergeable(struct pipe_buffer *buf);
extern const struct pipe_buf_operations nosteal_pipe_buf_ops;