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authorJann Horn <jannh@google.com>2019-01-23 15:19:17 +0100
committerAl Viro <viro@zeniv.linux.org.uk>2019-02-01 02:01:45 -0500
commita0ce2f0aa6ad97c3d4927bf2ca54bcebdf062d55 (patch)
tree69fa826572391147bebfa35abc51dd3a326b3e6a /fs/splice.c
parentfs: move generic stat response attr handling to vfs_getattr_nosec (diff)
downloadlinux-dev-a0ce2f0aa6ad97c3d4927bf2ca54bcebdf062d55.tar.xz
linux-dev-a0ce2f0aa6ad97c3d4927bf2ca54bcebdf062d55.zip
splice: don't merge into linked buffers
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>
Diffstat (limited to 'fs/splice.c')
-rw-r--r--fs/splice.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/splice.c b/fs/splice.c
index de2ede048473..90c29675d573 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1597,6 +1597,8 @@ retry:
*/
obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
+ pipe_buf_mark_unmergeable(obuf);
+
obuf->len = len;
opipe->nrbufs++;
ibuf->offset += obuf->len;
@@ -1671,6 +1673,8 @@ 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;