From 8cce437fbb5c1f2af2f63834fa05082596beca5d Mon Sep 17 00:00:00 2001 From: Philipp Rudo Date: Thu, 19 Jul 2018 11:13:45 +0200 Subject: [PATCH] s390/kdump: Fix elfcorehdr size calculation Before the memory for the elfcorehdr is allocated the required size is estimated with alloc_size = 0x1000 + get_cpu_cnt() * 0x4a0 + mem_chunk_cnt * sizeof(Elf64_Phdr); Where 0x4a0 is used as size for the ELF notes to store the register contend. This size is 8 bytes too small. Usually this does not immediately cause a problem because the page reserved for overhead (Elf_Ehdr, vmcoreinfo, etc.) is pretty generous. So usually there is enough spare memory to counter the mis-calculated per cpu size. However, with growing overhead and/or a huge cpu count the allocated size gets too small for the elfcorehdr. Ultimately a BUG_ON is triggered causing the crash kernel to panic. Fix this by properly calculating the required size instead of relying on magic numbers. Fixes: a62bc07392539 ("s390/kdump: add support for vector extension") Signed-off-by: Philipp Rudo Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/crash_dump.c | 104 ++++++++++++++++++++++++++++++++-- 1 file changed, 98 insertions(+), 6 deletions(-) diff --git a/arch/s390/kernel/crash_dump.c b/arch/s390/kernel/crash_dump.c index 9f5ea9d87069..c3620bafc374 100644 --- a/arch/s390/kernel/crash_dump.c +++ b/arch/s390/kernel/crash_dump.c @@ -306,6 +306,15 @@ static void *kzalloc_panic(int len) return rc; } +static const char *nt_name(Elf64_Word type) +{ + const char *name = "LINUX"; + + if (type == NT_PRPSINFO || type == NT_PRSTATUS || type == NT_PRFPREG) + name = KEXEC_CORE_NOTE_NAME; + return name; +} + /* * Initialize ELF note */ @@ -332,11 +341,26 @@ static void *nt_init_name(void *buf, Elf64_Word type, void *desc, int d_len, static inline void *nt_init(void *buf, Elf64_Word type, void *desc, int d_len) { - const char *note_name = "LINUX"; + return nt_init_name(buf, type, desc, d_len, nt_name(type)); +} - if (type == NT_PRPSINFO || type == NT_PRSTATUS || type == NT_PRFPREG) - note_name = KEXEC_CORE_NOTE_NAME; - return nt_init_name(buf, type, desc, d_len, note_name); +/* + * Calculate the size of ELF note + */ +static size_t nt_size_name(int d_len, const char *name) +{ + size_t size; + + size = sizeof(Elf64_Nhdr); + size += roundup(strlen(name) + 1, 4); + size += roundup(d_len, 4); + + return size; +} + +static inline size_t nt_size(Elf64_Word type, int d_len) +{ + return nt_size_name(d_len, nt_name(type)); } /* @@ -374,6 +398,29 @@ static void *fill_cpu_elf_notes(void *ptr, int cpu, struct save_area *sa) return ptr; } +/* + * Calculate size of ELF notes per cpu + */ +static size_t get_cpu_elf_notes_size(void) +{ + struct save_area *sa = NULL; + size_t size; + + size = nt_size(NT_PRSTATUS, sizeof(struct elf_prstatus)); + size += nt_size(NT_PRFPREG, sizeof(elf_fpregset_t)); + size += nt_size(NT_S390_TIMER, sizeof(sa->timer)); + size += nt_size(NT_S390_TODCMP, sizeof(sa->todcmp)); + size += nt_size(NT_S390_TODPREG, sizeof(sa->todpreg)); + size += nt_size(NT_S390_CTRS, sizeof(sa->ctrs)); + size += nt_size(NT_S390_PREFIX, sizeof(sa->prefix)); + if (MACHINE_HAS_VX) { + size += nt_size(NT_S390_VXRS_HIGH, sizeof(sa->vxrs_high)); + size += nt_size(NT_S390_VXRS_LOW, sizeof(sa->vxrs_low)); + } + + return size; +} + /* * Initialize prpsinfo note (new kernel) */ @@ -429,6 +476,30 @@ static void *nt_vmcoreinfo(void *ptr) return nt_init_name(ptr, 0, vmcoreinfo, size, "VMCOREINFO"); } +static size_t nt_vmcoreinfo_size(void) +{ + const char *name = "VMCOREINFO"; + char nt_name[11]; + Elf64_Nhdr note; + void *addr; + + if (copy_oldmem_kernel(&addr, &S390_lowcore.vmcore_info, sizeof(addr))) + return 0; + + if (copy_oldmem_kernel(¬e, addr, sizeof(note))) + return 0; + + memset(nt_name, 0, sizeof(nt_name)); + if (copy_oldmem_kernel(nt_name, addr + sizeof(note), + sizeof(nt_name) - 1)) + return 0; + + if (strcmp(nt_name, name) != 0) + return 0; + + return nt_size_name(note.n_descsz, name); +} + /* * Initialize final note (needed for /proc/vmcore code) */ @@ -539,6 +610,27 @@ static void *notes_init(Elf64_Phdr *phdr, void *ptr, u64 notes_offset) return ptr; } +static size_t get_elfcorehdr_size(int mem_chunk_cnt) +{ + size_t size; + + size = sizeof(Elf64_Ehdr); + /* PT_NOTES */ + size += sizeof(Elf64_Phdr); + /* nt_prpsinfo */ + size += nt_size(NT_PRPSINFO, sizeof(struct elf_prpsinfo)); + /* regsets */ + size += get_cpu_cnt() * get_cpu_elf_notes_size(); + /* nt_vmcoreinfo */ + size += nt_vmcoreinfo_size(); + /* nt_final */ + size += sizeof(Elf64_Nhdr); + /* PT_LOADS */ + size += mem_chunk_cnt * sizeof(Elf64_Phdr); + + return size; +} + /* * Create ELF core header (new kernel) */ @@ -566,8 +658,8 @@ int elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size) mem_chunk_cnt = get_mem_chunk_cnt(); - alloc_size = 0x1000 + get_cpu_cnt() * 0x4a0 + - mem_chunk_cnt * sizeof(Elf64_Phdr); + alloc_size = get_elfcorehdr_size(mem_chunk_cnt); + hdr = kzalloc_panic(alloc_size); /* Init elf header */ ptr = ehdr_init(hdr, mem_chunk_cnt);