From: Allen <allen.lkml@gmail.com>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: Allen Pais <apais@linux.microsoft.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, viro@zeniv.linux.org.uk, brauner@kernel.org,
jack@suse.cz, ebiederm@xmission.com, keescook@chromium.org,
j.granados@samsung.com
Subject: Re: [RFC PATCH] fs/coredump: Enable dynamic configuration of max file note size
Date: Tue, 30 Apr 2024 10:51:29 -0700 [thread overview]
Message-ID: <CAOMdWS+jSC5UoO9nqYvRe_rRid_SOSuzK3c8M-NJ9-LKVhoCFg@mail.gmail.com> (raw)
In-Reply-To: <CAOMdWS+u3WkB5yiwTjNKOD1sMSQP-F22FSpkq0R8TCPhihp=2w@mail.gmail.com>
> Will address it in v2.
>
> > If we're gonna do this, it makes sense to document the ELF note binary
> > limiations. Then, consider a defense too, what if a specially crafted
> > binary with a huge elf note are core dumped many times, what then?
> > Lifting to 4 MiB puts in a situation where abuse can lead to many silly
> > insane kvmalloc()s. Is that what we want? Why?
> >
> You raise a good point. I need to see how we can safely handle this case.
>
Luis,
Here's a rough idea that caps the max allowable size for the note section.
I am using 16MB as the max value.
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -56,10 +56,14 @@
static bool dump_vma_snapshot(struct coredump_params *cprm);
static void free_vma_snapshot(struct coredump_params *cprm);
+#define MAX_FILE_NOTE_SIZE (4*1024*1024)
+#define MAX_ALLOWED_NOTE_SIZE (16*1024*1024)
+
static int core_uses_pid;
static unsigned int core_pipe_limit;
static char core_pattern[CORENAME_MAX_SIZE] = "core";
static int core_name_size = CORENAME_MAX_SIZE;
+unsigned int core_file_note_size_max = MAX_FILE_NOTE_SIZE;
struct core_name {
char *corename;
@@ -1060,12 +1064,22 @@ static struct ctl_table coredump_sysctls[] = {
.mode = 0644,
.proc_handler = proc_dointvec,
},
+ {
+ .procname = "core_file_note_size_max",
+ .data = &core_file_note_size_max,
+ .maxlen = sizeof(unsigned int),
+ .mode = 0644,
+ .proc_handler = proc_core_file_note_size_max,
+ },
};
+int proc_core_file_note_size_max(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos) {
+ int error = proc_douintvec(table, write, buffer, lenp, ppos);
+ if (write && (core_file_note_size_max < MAX_FILE_NOTE_SIZE
+ || core_file_note_size_max > MAX_ALLOWED_NOTE_SIZE))
+. /* Revert to default if out of bounds */
+ core_file_note_size_max = MAX_FILE_NOTE_SIZE;
+ return error;
+}
Let me know what you think.
Thanks,
- Allen
next prev parent reply other threads:[~2024-04-30 17:51 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-29 17:21 [RFC PATCH] fs/coredump: Enable dynamic configuration of max file note size Allen Pais
2024-04-29 18:38 ` Luis Chamberlain
2024-04-29 22:32 ` Allen
2024-04-30 17:51 ` Allen [this message]
2024-04-29 19:49 ` Kees Cook
2024-04-29 22:35 ` Allen
2024-04-30 5:36 ` Kees Cook
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