From 00ec99da43a7c2aed46c6595aa271b84bb1b1462 Mon Sep 17 00:00:00 2001 From: Roland McGrath Date: Sun, 11 Nov 2007 19:13:43 -0800 Subject: core dump: remain dumpable The coredump code always calls set_dumpable(0) when it starts (even if RLIMIT_CORE prevents any core from being dumped). The effect of this (via task_dumpable) is to make /proc/pid/* files owned by root instead of the user, so the user can no longer examine his own process--in a case where there was never any privileged data to protect. This affects e.g. auxv, environ, fd; in Fedora (execshield) kernels, also maps. In practice, you can only notice this when a debugger has requested PTRACE_EVENT_EXIT tracing. set_dumpable was only used in do_coredump for synchronization and not intended for any security purpose. (It doesn't secure anything that wasn't already unsecured when a process dies by SIGTERM instead of SIGQUIT.) This changes do_coredump to check the core_waiters count as the means of synchronization, which is sufficient. Now we leave the "dumpable" bits alone. Signed-off-by: Roland McGrath Signed-off-by: Linus Torvalds --- fs/exec.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index 2c942e2d14ea..4ccaaa4b13b2 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1692,7 +1692,10 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs) if (!binfmt || !binfmt->core_dump) goto fail; down_write(&mm->mmap_sem); - if (!get_dumpable(mm)) { + /* + * If another thread got here first, or we are not dumpable, bail out. + */ + if (mm->core_waiters || !get_dumpable(mm)) { up_write(&mm->mmap_sem); goto fail; } @@ -1706,7 +1709,6 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs) flag = O_EXCL; /* Stop rewrite attacks */ current->fsuid = 0; /* Dump root private */ } - set_dumpable(mm, 0); retval = coredump_wait(exit_code); if (retval < 0) -- cgit v1.2.2