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List: busybox
Subject: [PATCH v2] echo: do not assume that free() leaves errno unmodified
From: Natanael Copa <ncopa () alpinelinux ! org>
Date: 2021-01-22 7:35:55
Message-ID: 20210122073555.2285-1-ncopa () alpinelinux ! org
[Download RAW message or body]
musl libc's mallocng free() may modify errno if kernel does not support
MADV_FREE which causes echo to echo with error when it shouldn't.
Future versions of POSIX[1] will require that free() leaves errno
unmodified but til then, do not rely free() implementation.
Should fix downstream issues:
https://github.com/alpinelinux/docker-alpine/issues/134
https://gitlab.alpinelinux.org/alpine/aports/-/issues/12311
Bloatcheck on x86_64:
function old new delta
echo_main 414 406 -8
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-8) Total: -8
bytes
text data bss dec hex filename
881114 15196 2000 898310 db506 busybox_old
881106 15196 2000 898302 db4fe busybox_unstripped
---
v2: do the free after bb_simple_perror_msg so it prints the correct
error message.
coreutils/echo.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/coreutils/echo.c b/coreutils/echo.c
index b3828894c..002832ead 100644
--- a/coreutils/echo.c
+++ b/coreutils/echo.c
@@ -97,6 +97,7 @@ int echo_main(int argc UNUSED_PARAM, char **argv)
#else
char nflag = 1;
char eflag = 0;
+ int err;
while ((arg = *++argv) != NULL) {
char n, e;
@@ -184,14 +185,12 @@ int echo_main(int argc UNUSED_PARAM, char **argv)
do_write:
/* Careful to error out on partial writes too (think ENOSPC!) */
- errno = 0;
- /*r =*/ full_write(STDOUT_FILENO, buffer, out - buffer);
- free(buffer);
- if (/*WRONG:r < 0*/ errno) {
+ err = full_write(STDOUT_FILENO, buffer, out - buffer) != out - buffer;
+ if (err) {
bb_simple_perror_msg(bb_msg_write_error);
- return 1;
}
- return 0;
+ free(buffer);
+ return err;
}
/*
--
2.30.0
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