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Date: Mon, 22 Nov 2021 09:55:29 +0800 From: Baoquan He <bhe@...hat.com> To: linux-kernel@...r.kernel.org Cc: kexec@...ts.infradead.org, dyoung@...hat.com, akpm@...ux-foundation.org Subject: Re: [PATCH 1/3] x86/kexec: fix memory leak of elf header buffer On 10/29/21 at 03:24pm, Baoquan He wrote: > This is reported by kmemleak detector: > > unreferenced object 0xffffc900002a9000 (size 4096): > comm "kexec", pid 14950, jiffies 4295110793 (age 373.951s) > hex dump (first 32 bytes): > 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 .ELF............ > 04 00 3e 00 01 00 00 00 00 00 00 00 00 00 00 00 ..>............. > backtrace: > [<0000000016a8ef9f>] __vmalloc_node_range+0x101/0x170 > [<000000002b66b6c0>] __vmalloc_node+0xb4/0x160 > [<00000000ad40107d>] crash_prepare_elf64_headers+0x8e/0xcd0 > [<0000000019afff23>] crash_load_segments+0x260/0x470 > [<0000000019ebe95c>] bzImage64_load+0x814/0xad0 > [<0000000093e16b05>] arch_kexec_kernel_image_load+0x1be/0x2a0 > [<000000009ef2fc88>] kimage_file_alloc_init+0x2ec/0x5a0 > [<0000000038f5a97a>] __do_sys_kexec_file_load+0x28d/0x530 > [<0000000087c19992>] do_syscall_64+0x3b/0x90 > [<0000000066e063a4>] entry_SYSCALL_64_after_hwframe+0x44/0xae > > In crash_prepare_elf64_headers(), a buffer is allocated via vmalloc() to > store elf headers. While it's not freed back to system correctly when > kdump kernel is reloaded or unloaded. Then memory leak is caused. > > Fix it by introducing x86 specific function > arch_kimage_file_post_load_cleanup(), and freeing the buffer there. > > Signed-off-by: Baoquan He <bhe@...hat.com> It deserves to add a Fixes tag, and this drawback exists since kexec_file_load added. It wastes one page of memory, or severa pages depending on the cpu numbers, not sure if it deserves to cc stable. Fixes: cb1052581e2b ("kexec: implementation of new syscall kexec_file_load") > --- > arch/x86/kernel/machine_kexec_64.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c > index 131f30fdcfbd..fd8223fa2de5 100644 > --- a/arch/x86/kernel/machine_kexec_64.c > +++ b/arch/x86/kernel/machine_kexec_64.c > @@ -511,6 +511,15 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi, > (int)ELF64_R_TYPE(rel[i].r_info), value); > return -ENOEXEC; > } > + > +int arch_kimage_file_post_load_cleanup(struct kimage *image) > +{ > + vfree(image->elf_headers); > + image->elf_headers = NULL; > + image->elf_headers_sz = 0; > + > + return kexec_image_post_load_cleanup_default(image); > +} > #endif /* CONFIG_KEXEC_FILE */ > > static int > -- > 2.17.2 >
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