From 08fc35f31b9e14cb4e8ba5bf43f824559dbdbe88 Mon Sep 17 00:00:00 2001 From: Stephen Brennan Date: Thu, 27 Oct 2022 13:50:08 -0700 Subject: [PATCH] vmcoreinfo: warn if we exceed vmcoreinfo data size Though vmcoreinfo is intended to be small, at just one page, useful information is still added to it, so we risk running out of space. Currently there is no runtime check to see whether the vmcoreinfo buffer has been exhausted. Add a warning for this case. Currently, my static checking tool[1] indicates that a good upper bound for vmcoreinfo size is currently 3415 bytes, but the best time to add warnings is before the risk becomes too high. [1] https://github.com/brenns10/kernel_stuff/blob/master/vmcoreinfosize/vmcoreinfosize.py Link: https://lkml.kernel.org/r/20221027205008.312534-1-stephen.s.brennan@oracle.com Signed-off-by: Stephen Brennan Acked-by: Baoquan He Cc: Dave Young Cc: Vivek Goyal Cc: Kees Cook Signed-off-by: Andrew Morton --- kernel/crash_core.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/crash_core.c b/kernel/crash_core.c index a0eb4d5cf557..87ef6096823f 100644 --- a/kernel/crash_core.c +++ b/kernel/crash_core.c @@ -383,6 +383,9 @@ void vmcoreinfo_append_str(const char *fmt, ...) memcpy(&vmcoreinfo_data[vmcoreinfo_size], buf, r); vmcoreinfo_size += r; + + WARN_ONCE(vmcoreinfo_size == VMCOREINFO_BYTES, + "vmcoreinfo data exceeds allocated size, truncating"); } /*