From c4bbafda70a0fc95c6595bffd6825ef264050d01 Mon Sep 17 00:00:00 2001 From: Alan Cox Date: Mon, 16 Apr 2007 22:53:13 -0700 Subject: [PATCH] exec.c: fix coredump to pipe problem and obscure "security hole" The patch checks for "|" in the pattern not the output and doesn't nail a pid on to a piped name (as it is a program name not a file) Also fixes a very very obscure security corner case. If you happen to have decided on a core pattern that starts with the program name then the user can run a program called "|myevilhack" as it stands. I doubt anyone does this. Signed-off-by: Alan Cox Confirmed-by: Christopher S. Aker Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/exec.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 7e36c6f6f53..3155e915307 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1244,13 +1244,17 @@ EXPORT_SYMBOL(set_binfmt); * name into corename, which must have space for at least * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator. */ -static void format_corename(char *corename, const char *pattern, long signr) +static int format_corename(char *corename, const char *pattern, long signr) { const char *pat_ptr = pattern; char *out_ptr = corename; char *const out_end = corename + CORENAME_MAX_SIZE; int rc; int pid_in_pattern = 0; + int ispipe = 0; + + if (*pattern == '|') + ispipe = 1; /* Repeat as long as we have more pattern to process and more output space */ @@ -1341,8 +1345,8 @@ static void format_corename(char *corename, const char *pattern, long signr) * * If core_pattern does not include a %p (as is the default) * and core_uses_pid is set, then .%pid will be appended to - * the filename */ - if (!pid_in_pattern + * the filename. Do not do this for piped commands. */ + if (!ispipe && !pid_in_pattern && (core_uses_pid || atomic_read(¤t->mm->mm_users) != 1)) { rc = snprintf(out_ptr, out_end - out_ptr, ".%d", current->tgid); @@ -1350,8 +1354,9 @@ static void format_corename(char *corename, const char *pattern, long signr) goto out; out_ptr += rc; } - out: +out: *out_ptr = 0; + return ispipe; } static void zap_process(struct task_struct *start) @@ -1502,16 +1507,15 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs) * uses lock_kernel() */ lock_kernel(); - format_corename(corename, core_pattern, signr); + ispipe = format_corename(corename, core_pattern, signr); unlock_kernel(); - if (corename[0] == '|') { + if (ispipe) { /* SIGPIPE can happen, but it's just never processed */ if(call_usermodehelper_pipe(corename+1, NULL, NULL, &file)) { printk(KERN_INFO "Core dump to %s pipe failed\n", corename); goto fail_unlock; } - ispipe = 1; } else file = filp_open(corename, O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,