From 7d75a96b15327050a294b1f54981781ce6e551e2 Mon Sep 17 00:00:00 2001 From: Denis Vlasenko Date: Thu, 22 Nov 2007 08:16:57 +0000 Subject: [PATCH] ash: fix bug where redirection of closed fd was leaving it open afterwards. redirect 983 1024 +41 bb_echo 276 301 +25 popredir 118 132 +14 evalcommand 1163 1176 +13 bbunpack 358 366 +8 echocmd 13 5 -8 echo_main 13 5 -8 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 5/2 up/down: 101/-16) Total: 85 bytes text data bss dec hex filename 774999 962 9236 785197 bfb2d busybox_old 775084 962 9236 785282 bfb82 busybox_unstripped --- coreutils/echo.c | 141 ++++++++++++++++++++++++++- include/libbb.h | 2 +- shell/ash.c | 35 ++++--- shell/ash_test/ash-redir/redir.right | 1 + shell/ash_test/ash-redir/redir.tests | 6 ++ 5 files changed, 169 insertions(+), 16 deletions(-) create mode 100644 shell/ash_test/ash-redir/redir.right create mode 100644 shell/ash_test/ash-redir/redir.tests diff --git a/coreutils/echo.c b/coreutils/echo.c index 860853f02..4c7a91743 100644 --- a/coreutils/echo.c +++ b/coreutils/echo.c @@ -25,7 +25,9 @@ #include "libbb.h" -int bb_echo(char **argv) +/* argc is unused, but removing it precludes compiler from + * using call -> jump optimization */ +int bb_echo(int argc, char **argv) { const char *arg; #if !ENABLE_FEATURE_FANCY_ECHO @@ -33,6 +35,18 @@ int bb_echo(char **argv) eflag = '\\', nflag = 1, /* 1 -- print '\n' */ }; + + /* We must check that stdout is not closed. + * The reason for this is highly non-obvious. + * bb_echo is used from shell. Shell must correctly handle "echo foo" + * if stdout is closed. With stdio, output gets shoveled into + * stdout buffer, and even fflush cannot clear it out. It seems that + * even if libc receives EBADF on write attempts, it feels determined + * to output data no matter what. So it will try later, + * and possibly will clobber future output. Not good. */ + if (dup2(1, 1) != 1) + return -1; + arg = *++argv; if (!arg) goto newline_ret; @@ -41,6 +55,10 @@ int bb_echo(char **argv) char nflag = 1; char eflag = 0; + /* We must check that stdout is not closed. */ + if (dup2(1, 1) != 1) + return -1; + while (1) { arg = *++argv; if (!arg) @@ -122,7 +140,7 @@ int bb_echo(char **argv) int echo_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int echo_main(int argc, char **argv) { - return bb_echo(argv); + return bb_echo(argc, argv); } /*- @@ -163,3 +181,122 @@ int echo_main(int argc, char **argv) * * @(#)echo.c 8.1 (Berkeley) 5/31/93 */ + +#ifdef VERSION_WITH_WRITEV +/* We can't use stdio. + * The reason for this is highly non-obvious. + * bb_echo is used from shell. Shell must correctly handle "echo foo" + * if stdout is closed. With stdio, output gets shoveled into + * stdout buffer, and even fflush cannot clear it out. It seems that + * even if libc receives EBADF on write attempts, it feels determined + * to output data no matter what. So it will try later, + * and possibly will clobber future output. Not good. + * + * Using writev instead, with 'direct' conversion of argv vector. + */ + +int bb_echo(int argc, char **argv) +{ + struct iovec io[argc]; + struct iovec *cur_io = io; + char *arg; + char *p; +#if !ENABLE_FEATURE_FANCY_ECHO + enum { + eflag = '\\', + nflag = 1, /* 1 -- print '\n' */ + }; + arg = *++argv; + if (!arg) + goto newline_ret; +#else + char nflag = 1; + char eflag = 0; + + while (1) { + arg = *++argv; + if (!arg) + goto newline_ret; + if (*arg != '-') + break; + + /* If it appears that we are handling options, then make sure + * that all of the options specified are actually valid. + * Otherwise, the string should just be echoed. + */ + p = arg + 1; + if (!*p) /* A single '-', so echo it. */ + goto just_echo; + + do { + if (!strrchr("neE", *p)) + goto just_echo; + } while (*++p); + + /* All of the options in this arg are valid, so handle them. */ + p = arg + 1; + do { + if (*p == 'n') + nflag = 0; + if (*p == 'e') + eflag = '\\'; + } while (*++p); + } + just_echo: +#endif + + while (1) { + /* arg is already == *argv and isn't NULL */ + int c; + + cur_io->iov_base = p = arg; + + if (!eflag) { + /* optimization for very common case */ + p += strlen(arg); + } else while ((c = *arg++)) { + if (c == eflag) { /* Check for escape seq. */ + if (*arg == 'c') { + /* '\c' means cancel newline and + * ignore all subsequent chars. */ + cur_io->iov_len = p - (char*)cur_io->iov_base; + cur_io++; + goto ret; + } +#if !ENABLE_FEATURE_FANCY_ECHO + /* SUSv3 specifies that octal escapes must begin with '0'. */ + if ( (((unsigned char)*arg) - '1') >= 7) +#endif + { + /* Since SUSv3 mandates a first digit of 0, 4-digit octals + * of the form \0### are accepted. */ + if (*arg == '0' && ((unsigned char)(arg[1]) - '0') < 8) { + arg++; + } + /* bb_process_escape_sequence can handle nul correctly */ + c = bb_process_escape_sequence( (void*) &arg); + } + } + *p++ = c; + } + + arg = *++argv; + if (arg) + *p++ = ' '; + cur_io->iov_len = p - (char*)cur_io->iov_base; + cur_io++; + if (!arg) + break; + } + + newline_ret: + if (nflag) { + cur_io->iov_base = (char*)"\n"; + cur_io->iov_len = 1; + cur_io++; + } + ret: + /* TODO: implement and use full_writev? */ + return writev(1, io, (cur_io - io)) >= 0; +} +#endif diff --git a/include/libbb.h b/include/libbb.h index 3bec43233..77392d09c 100644 --- a/include/libbb.h +++ b/include/libbb.h @@ -728,7 +728,7 @@ extern void bb_verror_msg(const char *s, va_list p, const char *strerr); /* applets which are useful from another applets */ int bb_cat(char** argv); -int bb_echo(char** argv); +int bb_echo(int argc, char** argv); int test_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int kill_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; #if ENABLE_ROUTE diff --git a/shell/ash.c b/shell/ash.c index bb930f55f..4113ce8e2 100644 --- a/shell/ash.c +++ b/shell/ash.c @@ -4567,6 +4567,7 @@ stoppedjobs(void) */ #define EMPTY -2 /* marks an unused slot in redirtab */ +#define CLOSED -3 /* marks a slot of previously-closed fd */ #ifndef PIPE_BUF # define PIPESIZE 4096 /* amount of buffering in a pipe */ #else @@ -4791,7 +4792,7 @@ redirect(union node *redir, int flags) int i; int fd; int newfd; - int *p; + nullredirs++; if (!redir) { return; @@ -4799,15 +4800,13 @@ redirect(union node *redir, int flags) sv = NULL; INT_OFF; if (flags & REDIR_PUSH) { - struct redirtab *q; - q = ckmalloc(sizeof(struct redirtab)); - q->next = redirlist; - redirlist = q; - q->nullredirs = nullredirs - 1; + sv = ckmalloc(sizeof(*sv)); + sv->next = redirlist; + redirlist = sv; + sv->nullredirs = nullredirs - 1; for (i = 0; i < 10; i++) - q->renamed[i] = EMPTY; + sv->renamed[i] = EMPTY; nullredirs = 0; - sv = q; } n = redir; do { @@ -4817,9 +4816,14 @@ redirect(union node *redir, int flags) continue; /* redirect from/to same file descriptor */ newfd = openredirect(n); - if (fd == newfd) + if (fd == newfd) { + /* Descriptor wasn't open before redirect. + * Mark it for close in the future */ + if (sv && sv->renamed[fd] == EMPTY) + sv->renamed[fd] = CLOSED; continue; - if (sv && *(p = &sv->renamed[fd]) == EMPTY) { + } + if (sv && sv->renamed[fd] == EMPTY) { i = fcntl(fd, F_DUPFD, 10); if (i == -1) { @@ -4831,7 +4835,7 @@ redirect(union node *redir, int flags) /* NOTREACHED */ } } else { - *p = i; + sv->renamed[fd] = i; close(fd); } } else { @@ -4840,7 +4844,7 @@ redirect(union node *redir, int flags) dupredirect(n, newfd); } while ((n = n->nfile.next)); INT_ON; - if (flags & REDIR_SAVEFD2 && sv && sv->renamed[2] >= 0) + if ((flags & REDIR_SAVEFD2) && sv && sv->renamed[2] >= 0) preverrout_fd = sv->renamed[2]; } @@ -4858,6 +4862,11 @@ popredir(int drop) INT_OFF; rp = redirlist; for (i = 0; i < 10; i++) { + if (rp->renamed[i] == CLOSED) { + if (!drop) + close(i); + continue; + } if (rp->renamed[i] != EMPTY) { if (!drop) { close(i); @@ -10994,7 +11003,7 @@ exitcmd(int argc, char **argv) static int echocmd(int argc, char **argv) { - return bb_echo(argv); + return bb_echo(argc, argv); } #endif diff --git a/shell/ash_test/ash-redir/redir.right b/shell/ash_test/ash-redir/redir.right new file mode 100644 index 000000000..2a02d41ce --- /dev/null +++ b/shell/ash_test/ash-redir/redir.right @@ -0,0 +1 @@ +TEST diff --git a/shell/ash_test/ash-redir/redir.tests b/shell/ash_test/ash-redir/redir.tests new file mode 100644 index 000000000..7a1a66806 --- /dev/null +++ b/shell/ash_test/ash-redir/redir.tests @@ -0,0 +1,6 @@ +# test: closed fds should stay closed +exec 1>&- +echo TEST >TEST +echo JUNK # lost: stdout is closed +cat TEST >&2 +rm TEST -- 2.25.1