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comm: close a race condition when comm is fed from stdin

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If one of the files has ended, we won't show the column, but we still
need to drain the file pointer to avoid potentially hitting a pipe
failure.

This commit moves the NULL offset checks inside show() so that getline()
and ferror() are still called on fp.

Reviewed by:	allanjude
Sponsored by:	Apple Inc.
Differential Revision:	https://reviews.freebsd.org/D45440
This commit is contained in:
Cosimo Cecchi 2024-06-06 16:51:43 +00:00 • committed by Allan Jude
parent 63f5c101a1
commit 7dd39ef4e0
1 changed files with 6 additions and 4 deletions
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10
usr.bin/comm/comm.c
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@ -129,12 +129,12 @@ main(int argc, char *argv[])
/* if one file done, display the rest of the other file */
if (n1 < 0) {
if (n2 >= 0 && col2 != NULL)
if (n2 >= 0)
show(fp2, argv[1], col2, &line2, &line2len);
break;
}
if (n2 < 0) {
if (n1 >= 0 && col1 != NULL)
if (n1 >= 0)
show(fp1, argv[0], col1, &line1, &line1len);
break;
}
@ -206,10 +206,12 @@ show(FILE *fp, const char *fn, const char *offset, char **bufp, size_t *buflenp)
ssize_t n;
do {
(void)printf("%s%s\n", offset, *bufp);
/* offset is NULL when draining fp, not printing */
if (offset != NULL)
(void)printf("%s%s\n", offset, *bufp);
if ((n = getline(bufp, buflenp, fp)) < 0)
break;
if (n > 0 && (*bufp)[n - 1] == '\n')
if (n > 0 && offset != NULL && (*bufp)[n - 1] == '\n')
(*bufp)[n - 1] = '\0';
} while (1);
if (ferror(fp))