diff options
author | Denys Vlasenko <vda.linux@googlemail.com> | 2016-08-19 19:23:56 +0300 |
---|---|---|
committer | Denys Vlasenko <vda.linux@googlemail.com> | 2016-08-19 19:43:06 +0300 |
commit | 215b0ca6e4fe466c6942d21a1bba62d97f2d5e5d (patch) | |
tree | 4fbb9563d870ce8a5f8f08015424e358a1462677 /shell/hush.c | |
parent | aedc3fe19fac368dc363050e0387d263b7e01cc6 (diff) |
hush: fix a bug in FEATURE_SH_STANDALONE=y config. Closes 9186
Run this in a "sh SCRIPT":
sha256sum /dev/null
echo END
sha256sum is a NOEXEC applet. It runs in a forked child. Then child exit()s.
By this time, entire script is read, and buffered in a FILE object
from fopen("SCRIPT"). But fgetc() did not consume entire input.
exit() lseeks back by -9 bytes, from <eof> to 'e' in 'echo'.
(this may be libc-specific).
This change of fd position *is shared with the parent*!
Now parent can read more, and it thinks there is another "echo END".
End result: two "echo END"s are run.
Fix this by _exit()ing instead.
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'shell/hush.c')
-rw-r--r-- | shell/hush.c | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/shell/hush.c b/shell/hush.c index ab192e2cd..be5c98a20 100644 --- a/shell/hush.c +++ b/shell/hush.c @@ -1580,11 +1580,11 @@ static void hush_exit(int exitcode) } #endif -#if ENABLE_HUSH_JOB fflush_all(); +#if ENABLE_HUSH_JOB sigexit(- (exitcode & 0xff)); #else - exit(exitcode); + _exit(exitcode); #endif } @@ -6466,7 +6466,23 @@ static void dump_cmd_in_x_mode(char **argv) * Never returns. * Don't exit() here. If you don't exec, use _exit instead. * The at_exit handlers apparently confuse the calling process, - * in particular stdin handling. Not sure why? -- because of vfork! (vda) */ + * in particular stdin handling. Not sure why? -- because of vfork! (vda) + * Also, it was observed that on exit(), fgetc'ed buffered data + * gets "unwound" by some libcs, via lseek(fd, -NUM, SEEK_CUR). + * With the net effect that even after fork(), not vfork(), + * exit() in NOEXECed applet in "sh SCRIPT": + * noexec_applet_here + * echo END_OF_SCRIPT + * lseeks fd in input FILE object from EOF to "e" in "echo END_OF_SCRIPT". + * This makes "echo END_OF_SCRIPT" executed twice. exexit() is the fix. + */ +#if ENABLE_FEATURE_SH_STANDALONE +static void exexit(void) +{ + fflush_all(); + _exit(xfunc_error_retval); +} +#endif static void pseudo_exec_argv(nommu_save_t *nommu_save, char **argv, int assignment_cnt, char **argv_expanded) NORETURN; @@ -6547,6 +6563,7 @@ static NOINLINE void pseudo_exec_argv(nommu_save_t *nommu_save, # if BB_MMU /* see above why on NOMMU it is not allowed */ if (APPLET_IS_NOEXEC(a)) { debug_printf_exec("running applet '%s'\n", argv[0]); + die_func = exexit; run_applet_no_and_exit(a, argv); } # endif |