Commit 39ec9eaa authored by Kees Cook's avatar Kees Cook
Browse files

coredump: Only sort VMAs when core_sort_vma sysctl is set 



The sorting of VMAs by size in commit 7d442a33 ("binfmt_elf: Dump
smaller VMAs first in ELF cores") breaks elfutils[1]. Instead, sort
based on the setting of the new sysctl, core_sort_vma, which defaults
to 0, no sorting.

Reported-by: default avatarMichael Stapelberg <michael@stapelberg.ch>
Closes: https://lore.kernel.org/all/20250218085407.61126-1-michael@stapelberg.de/

 [1]
Fixes: 7d442a33 ("binfmt_elf: Dump smaller VMAs first in ELF cores")
Signed-off-by: default avatarKees Cook <kees@kernel.org>
parent a64dcfb4

Documentation/admin-guide/sysctl/kernel.rst

+11 −0
Original line number Diff line number Diff line
@@ -212,6 +212,17 @@ pid>/``). 
This value defaults to 0.





core_sort_vma

=============



The default coredump writes VMAs in address order. By setting

``core_sort_vma`` to 1, VMAs will be written from smallest size

to largest size. This is known to break at least elfutils, but

can be handy when dealing with very large (and truncated)

coredumps where the more useful debugging details are included

in the smaller VMAs.





core_uses_pid

=============

fs/coredump.c

+13 −2
Original line number Diff line number Diff line
@@ -63,6 +63,7 @@ static void free_vma_snapshot(struct coredump_params *cprm); 


static int core_uses_pid;

static unsigned int core_pipe_limit;

static unsigned int core_sort_vma;

static char core_pattern[CORENAME_MAX_SIZE] = "core";

static int core_name_size = CORENAME_MAX_SIZE;

unsigned int core_file_note_size_limit = CORE_FILE_NOTE_SIZE_DEFAULT;
@@ -1026,6 +1027,15 @@ static const struct ctl_table coredump_sysctls[] = { 
		.extra1		= (unsigned int *)&core_file_note_size_min,

		.extra2		= (unsigned int *)&core_file_note_size_max,

	},

	{

		.procname	= "core_sort_vma",

		.data		= &core_sort_vma,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= proc_douintvec_minmax,

		.extra1		= SYSCTL_ZERO,

		.extra2		= SYSCTL_ONE,

	},

};



static int __init init_fs_coredump_sysctls(void)
@@ -1256,6 +1266,7 @@ static bool dump_vma_snapshot(struct coredump_params *cprm) 
		cprm->vma_data_size += m->dump_size;

	}



	if (core_sort_vma)

		sort(cprm->vma_meta, cprm->vma_count, sizeof(*cprm->vma_meta),

		     cmp_vma_size, NULL);