linux-kernel - Re: [PATCH v2] proc/vmcore: fix potential memory leak in vmcore

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Message-ID: <20220709001704.GA342876@MiWiFi-R3L-srv>
Date:   Sat, 9 Jul 2022 08:17:04 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Jianglei Nie <niejianglei2021@....com>, akpm@...ux-foundation.org
Cc:     vgoyal@...hat.com, dyoung@...hat.com, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v2] proc/vmcore: fix potential memory leak in
 vmcore_init()

On 07/08/22 at 04:34pm, Baoquan He wrote:
> On 07/04/22 at 04:18pm, Jianglei Nie wrote:
> > elfcorehdr_alloc() allocates a memory chunk for elfcorehdr_addr with
> > kzalloc(). If is_vmcore_usable() returns false, elfcorehdr_addr is a
> > predefined value. If parse_crash_elf_headers() occurs some error and
> > returns a negetive value, the elfcorehdr_addr should be released with
> > elfcorehdr_free().
> > 
> > We can fix by calling elfcorehdr_free() when parse_crash_elf_headers()
> > fails.
> 
> LGTM,
> 
> Acked-by: Baoquan He <bhe@...hat.com>

Sorry, I didn't check the code change carefully. This v2 is not right. I
thought Jianglei took my suggested code change directly. Seems he
mistakenly took part of them and caused error.

> 
> > 
> > Signed-off-by: Jianglei Nie <niejianglei2021@....com>
> > ---
> >  fs/proc/vmcore.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
> > index 4eaeb645e759..86887bd90263 100644
> > --- a/fs/proc/vmcore.c
> > +++ b/fs/proc/vmcore.c
> > @@ -1569,7 +1569,7 @@ static int __init vmcore_init(void)
> >  	rc = parse_crash_elf_headers();
> >  	if (rc) {
> >  		pr_warn("Kdump: vmcore not initialized\n");
> > -		return rc;
> > +		goto fail;
> >  	}
> >  	elfcorehdr_free(elfcorehdr_addr);
        ~~
        this line should be removed.
> >  	elfcorehdr_addr = ELFCORE_ADDR_ERR;
> > @@ -1577,6 +1577,9 @@ static int __init vmcore_init(void)
> >  	proc_vmcore = proc_create("vmcore", S_IRUSR, NULL, &vmcore_proc_ops);
> >  	if (proc_vmcore)
> >  		proc_vmcore->size = vmcore_size;
> > +
> > +fail:
> > +	elfcorehdr_free(elfcorehdr_addr);
> >  	return 0;
        ^
        return rc;  the returned value is wrong with v2.

What I suggested is as below. 

Andrew, please drop the one merged into mm-unstable branch.

Hi Jianglei,

Can you post v3 with below correct change and add Andrew to CC?

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 4eaeb645e759..390515c249dd 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -1569,15 +1569,16 @@ static int __init vmcore_init(void)
 	rc = parse_crash_elf_headers();
 	if (rc) {
 		pr_warn("Kdump: vmcore not initialized\n");
-		return rc;
+		goto fail;
 	}
-	elfcorehdr_free(elfcorehdr_addr);
 	elfcorehdr_addr = ELFCORE_ADDR_ERR;
 
 	proc_vmcore = proc_create("vmcore", S_IRUSR, NULL, &vmcore_proc_ops);
 	if (proc_vmcore)
 		proc_vmcore->size = vmcore_size;
-	return 0;
+fail:
+	elfcorehdr_free(elfcorehdr_addr);
+	return rc;
 }
 fs_initcall(vmcore_init);