Messages in this thread | | | From | Ian Rogers <> | Date | Mon, 12 Feb 2024 08:06:43 -0800 | Subject | Re: [PATCH v2 6/9] perf tests: Use scandirat for shell script finding |
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On Fri, Feb 9, 2024 at 8:41 PM Namhyung Kim <namhyung@kernel.org> wrote: > > On Wed, Jan 31, 2024 at 4:15 PM Ian Rogers <irogers@google.com> wrote: > > > > Avoid filename appending buffers by using openat, faccessat and > > scandirat more widely. Turn the script's path back to a file name > > using readlink from /proc/<pid>/fd/<fd>. > > > > Read the script's description using api/io.h to avoid fdopen > > conversions. Whilst reading perform additional sanity checks on the > > script's contents. > > > > Signed-off-by: Ian Rogers <irogers@google.com> > > --- > [SNIP] > > -static const char *shell_test__description(char *description, size_t size, > > - const char *path, const char *name) > > +static char *shell_test__description(int dir_fd, const char *name) > > { > > - FILE *fp; > > - char filename[PATH_MAX]; > > - int ch; > > + struct io io; > > + char buf[128], desc[256]; > > + int ch, pos = 0; > > > > - path__join(filename, sizeof(filename), path, name); > > - fp = fopen(filename, "r"); > > - if (!fp) > > + io__init(&io, openat(dir_fd, name, O_RDONLY), buf, sizeof(buf)); > > + if (io.fd < 0) > > return NULL; > > > > /* Skip first line - should be #!/bin/sh Shebang */ > > + if (io__get_char(&io) != '#') > > + goto err_out; > > + if (io__get_char(&io) != '!') > > + goto err_out; > > do { > > - ch = fgetc(fp); > > - } while (ch != EOF && ch != '\n'); > > - > > - description = fgets(description, size, fp); > > - fclose(fp); > > + ch = io__get_char(&io); > > + if (ch < 0) > > + goto err_out; > > + } while (ch != '\n'); > > > > - /* Assume first char on line is omment everything after that desc */ > > - return description ? strim(description + 1) : NULL; > > + do { > > + ch = io__get_char(&io); > > + if (ch < 0) > > + goto err_out; > > + } while (ch == '#' || isspace(ch)); > > + while (ch > 0 && ch != '\n') { > > + desc[pos++] = ch; > > + if (pos >= (int)sizeof(desc) - 1) > > Maybe (pos == sizeof(desc) - 2) ? I'm not sure what happens if it has a > description longer than the buffer size.
Thanks Namhyung!
sizeof(desc) - 1 == sizeof(char[256]) - 1 == 255 , so at this point pos can at most be 255 and there is one space after pos for a trailing '\0'.
> > + break; > > + ch = io__get_char(&io); > > + } > > + while (pos > 0 && isspace(desc[--pos])) > > + ;
Here pos is moved back to at least one to 254.
> > + desc[++pos] = '\0'; > > Wouldn't it overflow the buffer?
At this point pos can only have a maximum value of 255 which is within the bounds of desc.
Thanks, Ian
> Thanks, > Namhyung > > > > + close(io.fd); > > + return strdup(desc); > > +err_out: > > + close(io.fd); > > + return NULL; > > }
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