linux-kernel - [RFC, PATCH 3/4] elf_core_dump(): make offset calculation and writing processes explicit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20091215.114137.104035145.d.hatayama@jp.fujitsu.com>
Date:	Tue, 15 Dec 2009 11:41:37 +0900 (JST)
From:	Daisuke HATAYAMA <d.hatayama@...fujitsu.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...ux-foundation.org, jdike@...toit.com, tony.luck@...el.com,
	mhiramat@...hat.com
Subject: [RFC, PATCH 3/4] elf_core_dump(): make offset calculation and
 writing processes explicit

My next patch will change elf_core_dump() so that the produced
corefile may include section header table. But here is a problem.

If the corefile contains section header table, one needs to
write its file header to e_shoff field of the ELF header. It
is impossible to implement it while keeping the current
implementation.

Currently, writing operation for ELF header is done at very
early stage, where the file offset cannot be calculated. So,
one needs to choose which of the following ways:

 1. Seeking back to retry writing operation for ELF header
    after completing writing process for a whole part

 2. Making offset calculation process and writing process
    totally sequential

However, the clause 1. is not always possible, since one
cannot assume that dump_seek() function always supports
the seek in the minus direction. Consider no_llseek.

Therefore, this patch adopts the clause 2.

Signed-off-by: Daisuke HATAYAMA <d.hatayama@...fujitsu.com>
---
 fs/binfmt_elf.c |   24 +++++++++++++++---------
 1 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 9666a8a..cded1ba 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1935,6 +1935,7 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file, un
 	loff_t offset = 0, dataoff, foffset;
 	unsigned long mm_flags;
 	struct elf_note_info info;
+	struct elf_phdr *phdr4note = NULL;
 
 	/*
 	 * We no longer stop all VM operations.
@@ -1977,30 +1978,34 @@ static int elf_core_dump(long signr, struct pt_regs *regs, struct file *file, un
 	fs = get_fs();
 	set_fs(KERNEL_DS);
 
-	size += sizeof(*elf);
-	if (size > limit || !dump_write(file, elf, sizeof(*elf)))
-		goto end_coredump;
-
 	offset += sizeof(*elf);				/* Elf header */
 	offset += (segs + 1) * sizeof(struct elf_phdr); /* Program headers */
 	foffset = offset;
 
 	/* Write notes phdr entry */
 	{
-		struct elf_phdr phdr;
 		size_t sz = get_note_info_size(&info);
 
 		sz += elf_coredump_extra_notes_size();
 
-		fill_elf_note_phdr(&phdr, sz, offset);
-		offset += sz;
-		size += sizeof(phdr);
-		if (size > limit || !dump_write(file, &phdr, sizeof(phdr)))
+		phdr4note = kmalloc(sizeof(*phdr4note), GFP_KERNEL);
+		if (!phdr4note)
 			goto end_coredump;
+
+		fill_elf_note_phdr(phdr4note, sz, offset);
+		offset += sz;
 	}
 
 	dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);
 
+	size += sizeof(*elf);
+	if (size > limit || !dump_write(file, elf, sizeof(*elf)))
+		goto end_coredump;
+
+	size += sizeof(*phdr4note);
+	if (size > limit || !dump_write(file, phdr4note, sizeof(*phdr4note)))
+		goto end_coredump;
+
 	/*
 	 * We must use the same mm->flags while dumping core to avoid
 	 * inconsistency between the program headers and bodies, otherwise an
@@ -2079,6 +2084,7 @@ end_coredump:
 
 cleanup:
 	free_note_info(&info);
+	kfree(phdr4note);
 	kfree(elf);
 out:
 	return has_dumped;
-- 
1.6.5.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/