From: Philipp Rudo Date: Fri, 13 Apr 2018 22:36:39 +0000 (-0700) Subject: kernel/kexec_file.c: remove mis-use of sh_offset field during purgatory load X-Git-Tag: Ubuntu-5.2.0-15.16~4581^2~2 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=8da0b724959ccd3f8435214ebdaf1aef548967bb;p=mirror_ubuntu-eoan-kernel.git kernel/kexec_file.c: remove mis-use of sh_offset field during purgatory load The current code uses the sh_offset field in purgatory_info->sechdrs to store a pointer to the current load address of the section. Depending whether the section will be loaded or not this is either a pointer into purgatory_info->purgatory_buf or kexec_purgatory. This is not only a violation of the ELF standard but also makes the code very hard to understand as you cannot tell if the memory you are using is read-only or not. Remove this misuse and store the offset of the section in pugaroty_info->purgatory_buf in sh_offset. Link: http://lkml.kernel.org/r/20180321112751.22196-10-prudo@linux.vnet.ibm.com Signed-off-by: Philipp Rudo Acked-by: Dave Young Cc: AKASHI Takahiro Cc: Eric Biederman Cc: Heiko Carstens Cc: Ingo Molnar Cc: Martin Schwidefsky Cc: Michael Ellerman Cc: Thiago Jung Bauermann Cc: Vivek Goyal Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c index 63dea30c8e02..a5e55d832d0a 100644 --- a/arch/x86/kernel/machine_kexec_64.c +++ b/arch/x86/kernel/machine_kexec_64.c @@ -417,13 +417,15 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi, * rel[i].r_offset contains byte offset from beginning * of section to the storage unit affected. * - * This is location to update (->sh_offset). This is temporary - * buffer where section is currently loaded. This will finally - * be loaded to a different address later, pointed to by + * This is location to update. This is temporary buffer + * where section is currently loaded. This will finally be + * loaded to a different address later, pointed to by * ->sh_addr. kexec takes care of moving it * (kexec_load_segment()). */ - location = (void *)(section->sh_offset + rel[i].r_offset); + location = pi->purgatory_buf; + location += section->sh_offset; + location += rel[i].r_offset; /* Final address of the location */ address = section->sh_addr + rel[i].r_offset; diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index 7b63de8a89b6..269116fd932c 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -790,6 +790,10 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi, Elf_Shdr *sechdrs; int i; + /* + * The section headers in kexec_purgatory are read-only. In order to + * have them modifiable make a temporary copy. + */ sechdrs = vzalloc(pi->ehdr->e_shnum * sizeof(Elf_Shdr)); if (!sechdrs) return -ENOMEM; @@ -797,28 +801,6 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi, pi->ehdr->e_shnum * sizeof(Elf_Shdr)); pi->sechdrs = sechdrs; - /* - * We seem to have multiple copies of sections. First copy is which - * is embedded in kernel in read only section. Some of these sections - * will be copied to a temporary buffer and relocated. And these - * sections will finally be copied to their final destination at - * segment load time. - * - * Use ->sh_offset to reflect section address in memory. It will - * point to original read only copy if section is not allocatable. - * Otherwise it will point to temporary copy which will be relocated. - * - * Use ->sh_addr to contain final address of the section where it - * will go during execution time. - */ - for (i = 0; i < pi->ehdr->e_shnum; i++) { - if (sechdrs[i].sh_type == SHT_NOBITS) - continue; - - sechdrs[i].sh_offset = (unsigned long)pi->ehdr + - sechdrs[i].sh_offset; - } - offset = 0; bss_addr = kbuf->mem + kbuf->bufsz; kbuf->image->start = pi->ehdr->e_entry; @@ -847,17 +829,12 @@ static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi, kbuf->image->start += kbuf->mem + offset; } - src = (void *)sechdrs[i].sh_offset; + src = (void *)pi->ehdr + sechdrs[i].sh_offset; dst = pi->purgatory_buf + offset; memcpy(dst, src, sechdrs[i].sh_size); sechdrs[i].sh_addr = kbuf->mem + offset; - - /* - * This section got copied to temporary buffer. Update - * ->sh_offset accordingly. - */ - sechdrs[i].sh_offset = (unsigned long)dst; + sechdrs[i].sh_offset = offset; offset += sechdrs[i].sh_size; } @@ -1067,7 +1044,7 @@ int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name, return -EINVAL; } - sym_buf = (char *)sec->sh_offset + sym->st_value; + sym_buf = (char *)pi->purgatory_buf + sec->sh_offset + sym->st_value; if (get_value) memcpy((void *)buf, sym_buf, size);