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From: Yuntao Wang <ytcoode@gmail.com>
To: linux-kernel@vger.kernel.org,
	kexec@lists.infradead.org,
	x86@kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Baoquan He <bhe@redhat.com>,
	Vivek Goyal <vgoyal@redhat.com>,
	Dave Young <dyoung@redhat.com>,
	Hari Bathini <hbathini@linux.ibm.com>,
	Sean Christopherson <seanjc@google.com>,
	Takashi Iwai <tiwai@suse.de>,
	Yuntao Wang <ytcoode@gmail.com>
Subject: [PATCH 1/2] x86/crash: fix potential cmem->ranges array overflow
Date: Mon, 18 Dec 2023 16:19:14 +0800
Message-ID: <20231218081915.24120-2-ytcoode@gmail.com>
In-Reply-To: <20231218081915.24120-1-ytcoode@gmail.com>
References: <20231218081915.24120-1-ytcoode@gmail.com>
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The max_nr_ranges field of cmem allocated in crash_setup_memmap_entries()
is not initialized, its default value is 0.

When elfcorehdr is allocated from the middle of crashk_res due to any
potential reason, that is, `image->elf_load_addr > crashk_res.start &&
image->elf_load_addr + image->elf_headers_sz - 1 < crashk_res.end`,
executing memmap_exclude_ranges() will cause a range split to occur in
crash_exclude_mem_range(), which eventually leads to an overflow of the
cmem->ranges array.

Set cmem->max_nr_ranges to 1 to make crash_exclude_mem_range() return
-ENOMEM instead of causing cmem->ranges array overflow even when a split
happens.

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
---
 arch/x86/kernel/crash.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index c92d88680dbf..3be46f4b441e 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -282,10 +282,6 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
 	struct crash_memmap_data cmd;
 	struct crash_mem *cmem;
 
-	cmem = vzalloc(struct_size(cmem, ranges, 1));
-	if (!cmem)
-		return -ENOMEM;
-
 	memset(&cmd, 0, sizeof(struct crash_memmap_data));
 	cmd.params = params;
 
@@ -321,6 +317,11 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
 	}
 
 	/* Exclude some ranges from crashk_res and add rest to memmap */
+	cmem = vzalloc(struct_size(cmem, ranges, 1));
+	if (!cmem)
+		return -ENOMEM;
+	cmem->max_nr_ranges = 1;
+
 	ret = memmap_exclude_ranges(image, cmem, crashk_res.start, crashk_res.end);
 	if (ret)
 		goto out;
-- 
2.43.0