linux-kernel - [PATCH] exec: don't force_sigsegv processes with a pending fatal signal

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Message-ID: <20180719205334.GA23942@visor>
Date:   Thu, 19 Jul 2018 13:53:34 -0700
From:   Ivan Delalande <colona@...sta.com>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] exec: don't force_sigsegv processes with a pending fatal
 signal

We were seeing unexplained segfaults in coreutils processes and other
basic utilities that we tracked down to binfmt_elf failing to load
segments for ld.so. Digging further, the actual problem seems to occur
when a process gets sigkilled while it is still being loaded by the
kernel. In our case when _do_page_fault goes for a retry it will return
early as it first checks for fatal_signal_pending(), so load_elf_interp
also returns with error and as a result search_binary_handler will
force_sigsegv() which is pretty confusing as nothing actually failed
here.

Fixes: 19d860a140be ("handle suicide on late failure exits in execve() in search_binary_handler()")
Reference: https://lkml.org/lkml/2013/2/14/5
Signed-off-by: Ivan Delalande <colona@...sta.com>
---
 fs/exec.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/exec.c b/fs/exec.c
index 2d4e0075bd24..620d6489b61c 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1657,7 +1657,8 @@ int search_binary_handler(struct linux_binprm *bprm)
 		if (retval < 0 && !bprm->mm) {
 			/* we got to flush_old_exec() and failed after it */
 			read_unlock(&binfmt_lock);
-			force_sigsegv(SIGSEGV, current);
+			if (!fatal_signal_pending(current))
+				force_sigsegv(SIGSEGV, current);
 			return retval;
 		}
 		if (retval != -ENOEXEC || !bprm->file) {
-- 
2.18.0