linux-kernel - [PATCH] fs/binfmt_elf.c: fix GPF when dereferencing invalid interpreter

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Message-ID: <20190330140032.GA1527@vostro>
Date:   Sat, 30 Mar 2019 07:00:32 -0700
From:   Nikitas Angelinas <nikitas.angelinas@...il.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        syzbot+0d1fcd7268b21baced4a@...kaller.appspotmail.com
Cc:     nikitas.angelinas@...il.com
Subject: [PATCH] fs/binfmt_elf.c: fix GPF when dereferencing invalid
 interpreter

Syzkaller found an issue where an invalid interpreter pointer is
dereferenced in load_elf_binary()->allow_write_access(). Fix this by
jumping to a different label in the cleanup path.

This patch applies against the latest linux-next tree. I have not tested
that the patch addresses the issue, but it should, imho.

Signed-off-by: Nikitas Angelinas <nikitas.angelinas@...il.com>
Reported-by: syzbot+0d1fcd7268b21baced4a@...kaller.appspotmail.com
Fixes: 44e63c4a0263 ("fs/binfmt_elf.c: free PT_INTERP filename ASAP")
---
 fs/binfmt_elf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 51bc894..09e76b2 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -777,7 +777,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
 			kfree(elf_interpreter);
 			retval = PTR_ERR(interpreter);
 			if (IS_ERR(interpreter))
-				goto out_free_dentry;
+				goto out_free_ph;
 
 			/*
 			 * If the binary is not readable then enforce
-- 
2.10.0