linux-kernel - [PATCH] binfmt_elf: use vmalloc() for allocation of vma

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Date:   Mon, 21 Nov 2016 11:29:51 -0500
From:   Jason Baron <jbaron@...mai.com>
To:     akpm@...ux-foundation.org, viro@...iv.linux.org.uk
Cc:     js07.lee@...il.com, linux-kernel@...r.kernel.org
Subject: [PATCH] binfmt_elf: use vmalloc() for allocation of vma_filesz

We have observed page allocations failures of order 4 during core dump
while trying to allocate vma_filesz. This results in a useless core file
of size 0. To improve reliability use vmalloc().

Note that the vmalloc() allocation is bounded by sysctl_max_map_count,
which is 65,530 by default. So with a 4k page size, and 8 bytes per seg,
this is a max of 128 pages or an order 7 allocation. Other parts of the
core dump path, such as fill_files_note() are already using vmalloc()
for presumably similar reasons.

Signed-off-by: Jason Baron <jbaron@...mai.com>
---
 fs/binfmt_elf.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 2472af2798c7..e6c1bd443806 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -2204,7 +2204,9 @@ static int elf_core_dump(struct coredump_params *cprm)

 	dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE);

-	vma_filesz = kmalloc_array(segs - 1, sizeof(*vma_filesz), GFP_KERNEL);
+	if (segs - 1 > ULONG_MAX / sizeof(*vma_filesz))
+		goto end_coredump;
+	vma_filesz = vmalloc((segs - 1) * sizeof(*vma_filesz));
 	if (!vma_filesz)
 		goto end_coredump;

@@ -2311,7 +2313,7 @@ static int elf_core_dump(struct coredump_params *cprm)
 cleanup:
 	free_note_info(&info);
 	kfree(shdr4extnum);
-	kfree(vma_filesz);
+	vfree(vma_filesz);
 	kfree(phdr4note);
 	kfree(elf);
 out:
-- 
2.6.1