This patch makes socketpair() use error paths which do not rely on heavy-weight call to sys_close(): it's better to try to push the file descriptor to userspace before installing the socket file to the file descriptor, so that errors are catched earlier and being easier to handle.
Using sys_close() seems to be the exception, while writing the file descriptor before installing it look like it's more or less the norm: eg. except for code used in init/, error handling involve fput() and put_unused_fd(), but not sys_close(). This make socketpair() usage of sys_close() quite unusual. So it deserves to be replaced by the common pattern relying on fput() and put_unused_fd() just like, for example, the one used in pipe(2) or recvmsg(2). Three distinct error paths are still needed since calling fput() on file structure returned by sock_alloc_file() will implicitly call sock_release() on the associated socket structure. Cc: David S. Miller <da...@davemloft.net> Cc: Al Viro <v...@zeniv.linux.org.uk> Signed-off-by: Yann Droneaud <ydrone...@opteya.com> Link: http://marc.info/?i=1385979146-13825-1-git-send-email-ydrone...@opteya.com --- Hi David, Please find a patch which was discussed last week. I've rework a bit the commit message to sum up our discussion about the pattern to use when dealing with file descriptor when it has to be copied to userspace. Regards. Changes from v2 [1]: - rework a bit commit message Changes from v1 [2]: - use three different error path to handle file allocated through sock_alloc_file(). Regards. [1] http://mid.gmane.org/1385979146-13825-1-git-send-email-ydrone...@opteya.com [2] http://mid.gmane.org/1385977019-12282-1-git-send-email-ydrone...@opteya.com net/socket.c | 49 +++++++++++++++++++++++++++++++------------------ 1 file changed, 31 insertions(+), 18 deletions(-) diff --git a/net/socket.c b/net/socket.c index cd38a785f7d2..879933aaed4c 100644 --- a/net/socket.c +++ b/net/socket.c @@ -1445,48 +1445,61 @@ SYSCALL_DEFINE4(socketpair, int, family, int, type, int, protocol, err = fd1; goto out_release_both; } + fd2 = get_unused_fd_flags(flags); if (unlikely(fd2 < 0)) { err = fd2; - put_unused_fd(fd1); - goto out_release_both; + goto out_put_unused_1; } newfile1 = sock_alloc_file(sock1, flags, NULL); if (unlikely(IS_ERR(newfile1))) { err = PTR_ERR(newfile1); - put_unused_fd(fd1); - put_unused_fd(fd2); - goto out_release_both; + goto out_put_unused_both; } newfile2 = sock_alloc_file(sock2, flags, NULL); if (IS_ERR(newfile2)) { err = PTR_ERR(newfile2); - fput(newfile1); - put_unused_fd(fd1); - put_unused_fd(fd2); - sock_release(sock2); - goto out; + goto out_fput_1; } + err = put_user(fd1, &usockvec[0]); + if (err) + goto out_fput_both; + + err = put_user(fd2, &usockvec[1]); + if (err) + goto out_fput_both; + audit_fd_pair(fd1, fd2); + fd_install(fd1, newfile1); fd_install(fd2, newfile2); /* fd1 and fd2 may be already another descriptors. * Not kernel problem. */ - err = put_user(fd1, &usockvec[0]); - if (!err) - err = put_user(fd2, &usockvec[1]); - if (!err) - return 0; + return 0; - sys_close(fd2); - sys_close(fd1); - return err; +out_fput_both: + fput(newfile2); + fput(newfile1); + put_unused_fd(fd2); + put_unused_fd(fd1); + goto out; + +out_fput_1: + fput(newfile1); + put_unused_fd(fd2); + put_unused_fd(fd1); + sock_release(sock2); + goto out; +out_put_unused_both: + put_unused_fd(fd2); +out_put_unused_1: + put_unused_fd(fd1); out_release_both: sock_release(sock2); out_release_1: -- 1.8.4.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
