1 files changed, 248 insertions, 287 deletions

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index e64ecb9f2720..ad72261ee3fe 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -10,6 +10,7 @@
  *	Safe accesses to vmalloc/direct-mapped discontiguous areas, Kanoj Sarcar <kanoj@sgi.com>
  */
 
+#include <linux/crash_core.h>
 #include <linux/mm.h>
 #include <linux/proc_fs.h>
 #include <linux/kcore.h>
@@ -49,32 +50,23 @@ static struct proc_dir_entry *proc_root_kcore;
 #define	kc_offset_to_vaddr(o) ((o) + PAGE_OFFSET)
 #endif
 
-/* An ELF note in memory */
-struct memelfnote
-{
-	const char *name;
-	int type;
-	unsigned int datasz;
-	void *data;
-};
-
 static LIST_HEAD(kclist_head);
-static DEFINE_RWLOCK(kclist_lock);
+static DECLARE_RWSEM(kclist_lock);
 static int kcore_need_update = 1;
 
-void
-kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
+/* This doesn't grab kclist_lock, so it should only be used at init time. */
+void __init kclist_add(struct kcore_list *new, void *addr, size_t size,
+		       int type)
 {
 	new->addr = (unsigned long)addr;
 	new->size = size;
 	new->type = type;
 
-	write_lock(&kclist_lock);
 	list_add_tail(&new->list, &kclist_head);
-	write_unlock(&kclist_lock);
 }
 
-static size_t get_kcore_size(int *nphdr, size_t *elf_buflen)
+static size_t get_kcore_size(int *nphdr, size_t *phdrs_len, size_t *notes_len,
+			     size_t *data_offset)
 {
 	size_t try, size;
 	struct kcore_list *m;
@@ -88,53 +80,19 @@ static size_t get_kcore_size(int *nphdr, size_t *elf_buflen)
 			size = try;
 		*nphdr = *nphdr + 1;
 	}
-	*elf_buflen =	sizeof(struct elfhdr) + 
-			(*nphdr + 2)*sizeof(struct elf_phdr) + 
-			3 * ((sizeof(struct elf_note)) +
-			     roundup(sizeof(CORE_STR), 4)) +
-			roundup(sizeof(struct elf_prstatus), 4) +
-			roundup(sizeof(struct elf_prpsinfo), 4) +
-			roundup(arch_task_struct_size, 4);
-	*elf_buflen = PAGE_ALIGN(*elf_buflen);
-	return size + *elf_buflen;
-}
-
-static void free_kclist_ents(struct list_head *head)
-{
-	struct kcore_list *tmp, *pos;
 
-	list_for_each_entry_safe(pos, tmp, head, list) {
-		list_del(&pos->list);
-		kfree(pos);
-	}
+	*phdrs_len = *nphdr * sizeof(struct elf_phdr);
+	*notes_len = (4 * sizeof(struct elf_note) +
+		      3 * ALIGN(sizeof(CORE_STR), 4) +
+		      VMCOREINFO_NOTE_NAME_BYTES +
+		      ALIGN(sizeof(struct elf_prstatus), 4) +
+		      ALIGN(sizeof(struct elf_prpsinfo), 4) +
+		      ALIGN(arch_task_struct_size, 4) +
+		      ALIGN(vmcoreinfo_size, 4));
+	*data_offset = PAGE_ALIGN(sizeof(struct elfhdr) + *phdrs_len +
+				  *notes_len);
+	return *data_offset + size;
 }
-/*
- * Replace all KCORE_RAM/KCORE_VMEMMAP information with passed list.
- */
-static void __kcore_update_ram(struct list_head *list)
-{
-	int nphdr;
-	size_t size;
-	struct kcore_list *tmp, *pos;
-	LIST_HEAD(garbage);
-
-	write_lock(&kclist_lock);
-	if (kcore_need_update) {
-		list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
-			if (pos->type == KCORE_RAM
-				|| pos->type == KCORE_VMEMMAP)
-				list_move(&pos->list, &garbage);
-		}
-		list_splice_tail(list, &kclist_head);
-	} else
-		list_splice(list, &garbage);
-	kcore_need_update = 0;
-	proc_root_kcore->size = get_kcore_size(&nphdr, &size);
-	write_unlock(&kclist_lock);
-
-	free_kclist_ents(&garbage);
-}
-
 
 #ifdef CONFIG_HIGHMEM
 /*
@@ -142,11 +100,9 @@ static void __kcore_update_ram(struct list_head *list)
  * because memory hole is not as big as !HIGHMEM case.
  * (HIGHMEM is special because part of memory is _invisible_ from the kernel.)
  */
-static int kcore_update_ram(void)
+static int kcore_ram_list(struct list_head *head)
 {
-	LIST_HEAD(head);
 	struct kcore_list *ent;
-	int ret = 0;
 
 	ent = kmalloc(sizeof(*ent), GFP_KERNEL);
 	if (!ent)
@@ -154,9 +110,8 @@ static int kcore_update_ram(void)
 	ent->addr = (unsigned long)__va(0);
 	ent->size = max_low_pfn << PAGE_SHIFT;
 	ent->type = KCORE_RAM;
-	list_add(&ent->list, &head);
-	__kcore_update_ram(&head);
-	return ret;
+	list_add(&ent->list, head);
+	return 0;
 }
 
 #else /* !CONFIG_HIGHMEM */
@@ -255,11 +210,10 @@ free_out:
 	return 1;
 }
 
-static int kcore_update_ram(void)
+static int kcore_ram_list(struct list_head *list)
 {
 	int nid, ret;
 	unsigned long end_pfn;
-	LIST_HEAD(head);
 
 	/* Not inialized....update now */
 	/* find out "max pfn" */
@@ -271,258 +225,258 @@ static int kcore_update_ram(void)
 			end_pfn = node_end;
 	}
 	/* scan 0 to max_pfn */
-	ret = walk_system_ram_range(0, end_pfn, &head, kclist_add_private);
-	if (ret) {
-		free_kclist_ents(&head);
+	ret = walk_system_ram_range(0, end_pfn, list, kclist_add_private);
+	if (ret)
 		return -ENOMEM;
-	}
-	__kcore_update_ram(&head);
-	return ret;
+	return 0;
 }
 #endif /* CONFIG_HIGHMEM */
 
-/*****************************************************************************/
-/*
- * determine size of ELF note
- */
-static int notesize(struct memelfnote *en)
-{
-	int sz;
-
-	sz = sizeof(struct elf_note);
-	sz += roundup((strlen(en->name) + 1), 4);
-	sz += roundup(en->datasz, 4);
-
-	return sz;
-} /* end notesize() */
-
-/*****************************************************************************/
-/*
- * store a note in the header buffer
- */
-static char *storenote(struct memelfnote *men, char *bufp)
+static int kcore_update_ram(void)
 {
-	struct elf_note en;
-
-#define DUMP_WRITE(addr,nr) do { memcpy(bufp,addr,nr); bufp += nr; } while(0)
-
-	en.n_namesz = strlen(men->name) + 1;
-	en.n_descsz = men->datasz;
-	en.n_type = men->type;
-
-	DUMP_WRITE(&en, sizeof(en));
-	DUMP_WRITE(men->name, en.n_namesz);
-
-	/* XXX - cast from long long to long to avoid need for libgcc.a */
-	bufp = (char*) roundup((unsigned long)bufp,4);
-	DUMP_WRITE(men->data, men->datasz);
-	bufp = (char*) roundup((unsigned long)bufp,4);
-
-#undef DUMP_WRITE
-
-	return bufp;
-} /* end storenote() */
+	LIST_HEAD(list);
+	LIST_HEAD(garbage);
+	int nphdr;
+	size_t phdrs_len, notes_len, data_offset;
+	struct kcore_list *tmp, *pos;
+	int ret = 0;
 
-/*
- * store an ELF coredump header in the supplied buffer
- * nphdr is the number of elf_phdr to insert
- */
-static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff)
-{
-	struct elf_prstatus prstatus;	/* NT_PRSTATUS */
-	struct elf_prpsinfo prpsinfo;	/* NT_PRPSINFO */
-	struct elf_phdr *nhdr, *phdr;
-	struct elfhdr *elf;
-	struct memelfnote notes[3];
-	off_t offset = 0;
-	struct kcore_list *m;
+	down_write(&kclist_lock);
+	if (!xchg(&kcore_need_update, 0))
+		goto out;
 
-	/* setup ELF header */
-	elf = (struct elfhdr *) bufp;
-	bufp += sizeof(struct elfhdr);
-	offset += sizeof(struct elfhdr);
-	memcpy(elf->e_ident, ELFMAG, SELFMAG);
-	elf->e_ident[EI_CLASS]	= ELF_CLASS;
-	elf->e_ident[EI_DATA]	= ELF_DATA;
-	elf->e_ident[EI_VERSION]= EV_CURRENT;
-	elf->e_ident[EI_OSABI] = ELF_OSABI;
-	memset(elf->e_ident+EI_PAD, 0, EI_NIDENT-EI_PAD);
-	elf->e_type	= ET_CORE;
-	elf->e_machine	= ELF_ARCH;
-	elf->e_version	= EV_CURRENT;
-	elf->e_entry	= 0;
-	elf->e_phoff	= sizeof(struct elfhdr);
-	elf->e_shoff	= 0;
-	elf->e_flags	= ELF_CORE_EFLAGS;
-	elf->e_ehsize	= sizeof(struct elfhdr);
-	elf->e_phentsize= sizeof(struct elf_phdr);
-	elf->e_phnum	= nphdr;
-	elf->e_shentsize= 0;
-	elf->e_shnum	= 0;
-	elf->e_shstrndx	= 0;
-
-	/* setup ELF PT_NOTE program header */
-	nhdr = (struct elf_phdr *) bufp;
-	bufp += sizeof(struct elf_phdr);
-	offset += sizeof(struct elf_phdr);
-	nhdr->p_type	= PT_NOTE;
-	nhdr->p_offset	= 0;
-	nhdr->p_vaddr	= 0;
-	nhdr->p_paddr	= 0;
-	nhdr->p_filesz	= 0;
-	nhdr->p_memsz	= 0;
-	nhdr->p_flags	= 0;
-	nhdr->p_align	= 0;
-
-	/* setup ELF PT_LOAD program header for every area */
-	list_for_each_entry(m, &kclist_head, list) {
-		phdr = (struct elf_phdr *) bufp;
-		bufp += sizeof(struct elf_phdr);
-		offset += sizeof(struct elf_phdr);
-
-		phdr->p_type	= PT_LOAD;
-		phdr->p_flags	= PF_R|PF_W|PF_X;
-		phdr->p_offset	= kc_vaddr_to_offset(m->addr) + dataoff;
-		phdr->p_vaddr	= (size_t)m->addr;
-		if (m->type == KCORE_RAM || m->type == KCORE_TEXT)
-			phdr->p_paddr	= __pa(m->addr);
-		else
-			phdr->p_paddr	= (elf_addr_t)-1;
-		phdr->p_filesz	= phdr->p_memsz	= m->size;
-		phdr->p_align	= PAGE_SIZE;
+	ret = kcore_ram_list(&list);
+	if (ret) {
+		/* Couldn't get the RAM list, try again next time. */
+		WRITE_ONCE(kcore_need_update, 1);
+		list_splice_tail(&list, &garbage);
+		goto out;
 	}
 
-	/*
-	 * Set up the notes in similar form to SVR4 core dumps made
-	 * with info from their /proc.
-	 */
-	nhdr->p_offset	= offset;
-
-	/* set up the process status */
-	notes[0].name = CORE_STR;
-	notes[0].type = NT_PRSTATUS;
-	notes[0].datasz = sizeof(struct elf_prstatus);
-	notes[0].data = &prstatus;
-
-	memset(&prstatus, 0, sizeof(struct elf_prstatus));
-
-	nhdr->p_filesz	= notesize(&notes[0]);
-	bufp = storenote(&notes[0], bufp);
-
-	/* set up the process info */
-	notes[1].name	= CORE_STR;
-	notes[1].type	= NT_PRPSINFO;
-	notes[1].datasz	= sizeof(struct elf_prpsinfo);
-	notes[1].data	= &prpsinfo;
-
-	memset(&prpsinfo, 0, sizeof(struct elf_prpsinfo));
-	prpsinfo.pr_state	= 0;
-	prpsinfo.pr_sname	= 'R';
-	prpsinfo.pr_zomb	= 0;
-
-	strcpy(prpsinfo.pr_fname, "vmlinux");
-	strlcpy(prpsinfo.pr_psargs, saved_command_line, sizeof(prpsinfo.pr_psargs));
-
-	nhdr->p_filesz	+= notesize(&notes[1]);
-	bufp = storenote(&notes[1], bufp);
+	list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
+		if (pos->type == KCORE_RAM || pos->type == KCORE_VMEMMAP)
+			list_move(&pos->list, &garbage);
+	}
+	list_splice_tail(&list, &kclist_head);
 
-	/* set up the task structure */
-	notes[2].name	= CORE_STR;
-	notes[2].type	= NT_TASKSTRUCT;
-	notes[2].datasz	= arch_task_struct_size;
-	notes[2].data	= current;
+	proc_root_kcore->size = get_kcore_size(&nphdr, &phdrs_len, &notes_len,
+					       &data_offset);
 
-	nhdr->p_filesz	+= notesize(&notes[2]);
-	bufp = storenote(&notes[2], bufp);
+out:
+	up_write(&kclist_lock);
+	list_for_each_entry_safe(pos, tmp, &garbage, list) {
+		list_del(&pos->list);
+		kfree(pos);
+	}
+	return ret;
+}
 
-} /* end elf_kcore_store_hdr() */
+static void append_kcore_note(char *notes, size_t *i, const char *name,
+			      unsigned int type, const void *desc,
+			      size_t descsz)
+{
+	struct elf_note *note = (struct elf_note *)&notes[*i];
+
+	note->n_namesz = strlen(name) + 1;
+	note->n_descsz = descsz;
+	note->n_type = type;
+	*i += sizeof(*note);
+	memcpy(&notes[*i], name, note->n_namesz);
+	*i = ALIGN(*i + note->n_namesz, 4);
+	memcpy(&notes[*i], desc, descsz);
+	*i = ALIGN(*i + descsz, 4);
+}
 
-/*****************************************************************************/
-/*
- * read from the ELF header and then kernel memory
- */
 static ssize_t
 read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 {
 	char *buf = file->private_data;
-	ssize_t acc = 0;
-	size_t size, tsz;
-	size_t elf_buflen;
+	size_t phdrs_offset, notes_offset, data_offset;
+	size_t phdrs_len, notes_len;
+	struct kcore_list *m;
+	size_t tsz;
 	int nphdr;
 	unsigned long start;
+	size_t orig_buflen = buflen;
+	int ret = 0;
 
-	read_lock(&kclist_lock);
-	size = get_kcore_size(&nphdr, &elf_buflen);
+	down_read(&kclist_lock);
+
+	get_kcore_size(&nphdr, &phdrs_len, &notes_len, &data_offset);
+	phdrs_offset = sizeof(struct elfhdr);
+	notes_offset = phdrs_offset + phdrs_len;
+
+	/* ELF file header. */
+	if (buflen && *fpos < sizeof(struct elfhdr)) {
+		struct elfhdr ehdr = {
+			.e_ident = {
+				[EI_MAG0] = ELFMAG0,
+				[EI_MAG1] = ELFMAG1,
+				[EI_MAG2] = ELFMAG2,
+				[EI_MAG3] = ELFMAG3,
+				[EI_CLASS] = ELF_CLASS,
+				[EI_DATA] = ELF_DATA,
+				[EI_VERSION] = EV_CURRENT,
+				[EI_OSABI] = ELF_OSABI,
+			},
+			.e_type = ET_CORE,
+			.e_machine = ELF_ARCH,
+			.e_version = EV_CURRENT,
+			.e_phoff = sizeof(struct elfhdr),
+			.e_flags = ELF_CORE_EFLAGS,
+			.e_ehsize = sizeof(struct elfhdr),
+			.e_phentsize = sizeof(struct elf_phdr),
+			.e_phnum = nphdr,
+		};
+
+		tsz = min_t(size_t, buflen, sizeof(struct elfhdr) - *fpos);
+		if (copy_to_user(buffer, (char *)&ehdr + *fpos, tsz)) {
+			ret = -EFAULT;
+			goto out;
+		}
 
-	if (buflen == 0 || *fpos >= size) {
-		read_unlock(&kclist_lock);
-		return 0;
+		buffer += tsz;
+		buflen -= tsz;
+		*fpos += tsz;
 	}
 
-	/* trim buflen to not go beyond EOF */
-	if (buflen > size - *fpos)
-		buflen = size - *fpos;
-
-	/* construct an ELF core header if we'll need some of it */
-	if (*fpos < elf_buflen) {
-		char * elf_buf;
-
-		tsz = elf_buflen - *fpos;
-		if (buflen < tsz)
-			tsz = buflen;
-		elf_buf = kzalloc(elf_buflen, GFP_ATOMIC);
-		if (!elf_buf) {
-			read_unlock(&kclist_lock);
-			return -ENOMEM;
+	/* ELF program headers. */
+	if (buflen && *fpos < phdrs_offset + phdrs_len) {
+		struct elf_phdr *phdrs, *phdr;
+
+		phdrs = kzalloc(phdrs_len, GFP_KERNEL);
+		if (!phdrs) {
+			ret = -ENOMEM;
+			goto out;
 		}
-		elf_kcore_store_hdr(elf_buf, nphdr, elf_buflen);
-		read_unlock(&kclist_lock);
-		if (copy_to_user(buffer, elf_buf + *fpos, tsz)) {
-			kfree(elf_buf);
-			return -EFAULT;
+
+		phdrs[0].p_type = PT_NOTE;
+		phdrs[0].p_offset = notes_offset;
+		phdrs[0].p_filesz = notes_len;
+
+		phdr = &phdrs[1];
+		list_for_each_entry(m, &kclist_head, list) {
+			phdr->p_type = PT_LOAD;
+			phdr->p_flags = PF_R | PF_W | PF_X;
+			phdr->p_offset = kc_vaddr_to_offset(m->addr) + data_offset;
+			if (m->type == KCORE_REMAP)
+				phdr->p_vaddr = (size_t)m->vaddr;
+			else
+				phdr->p_vaddr = (size_t)m->addr;
+			if (m->type == KCORE_RAM || m->type == KCORE_REMAP)
+				phdr->p_paddr = __pa(m->addr);
+			else if (m->type == KCORE_TEXT)
+				phdr->p_paddr = __pa_symbol(m->addr);
+			else
+				phdr->p_paddr = (elf_addr_t)-1;
+			phdr->p_filesz = phdr->p_memsz = m->size;
+			phdr->p_align = PAGE_SIZE;
+			phdr++;
 		}
-		kfree(elf_buf);
+
+		tsz = min_t(size_t, buflen, phdrs_offset + phdrs_len - *fpos);
+		if (copy_to_user(buffer, (char *)phdrs + *fpos - phdrs_offset,
+				 tsz)) {
+			kfree(phdrs);
+			ret = -EFAULT;
+			goto out;
+		}
+		kfree(phdrs);
+
+		buffer += tsz;
 		buflen -= tsz;
 		*fpos += tsz;
-		buffer += tsz;
-		acc += tsz;
+	}
+
+	/* ELF note segment. */
+	if (buflen && *fpos < notes_offset + notes_len) {
+		struct elf_prstatus prstatus = {};
+		struct elf_prpsinfo prpsinfo = {
+			.pr_sname = 'R',
+			.pr_fname = "vmlinux",
+		};
+		char *notes;
+		size_t i = 0;
+
+		strlcpy(prpsinfo.pr_psargs, saved_command_line,
+			sizeof(prpsinfo.pr_psargs));
+
+		notes = kzalloc(notes_len, GFP_KERNEL);
+		if (!notes) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		append_kcore_note(notes, &i, CORE_STR, NT_PRSTATUS, &prstatus,
+				  sizeof(prstatus));
+		append_kcore_note(notes, &i, CORE_STR, NT_PRPSINFO, &prpsinfo,
+				  sizeof(prpsinfo));
+		append_kcore_note(notes, &i, CORE_STR, NT_TASKSTRUCT, current,
+				  arch_task_struct_size);
+		/*
+		 * vmcoreinfo_size is mostly constant after init time, but it
+		 * can be changed by crash_save_vmcoreinfo(). Racing here with a
+		 * panic on another CPU before the machine goes down is insanely
+		 * unlikely, but it's better to not leave potential buffer
+		 * overflows lying around, regardless.
+		 */
+		append_kcore_note(notes, &i, VMCOREINFO_NOTE_NAME, 0,
+				  vmcoreinfo_data,
+				  min(vmcoreinfo_size, notes_len - i));
+
+		tsz = min_t(size_t, buflen, notes_offset + notes_len - *fpos);
+		if (copy_to_user(buffer, notes + *fpos - notes_offset, tsz)) {
+			kfree(notes);
+			ret = -EFAULT;
+			goto out;
+		}
+		kfree(notes);
 
-		/* leave now if filled buffer already */
-		if (buflen == 0)
-			return acc;
-	} else
-		read_unlock(&kclist_lock);
+		buffer += tsz;
+		buflen -= tsz;
+		*fpos += tsz;
+	}
 
 	/*
 	 * Check to see if our file offset matches with any of
 	 * the addresses in the elf_phdr on our list.
 	 */
-	start = kc_offset_to_vaddr(*fpos - elf_buflen);
+	start = kc_offset_to_vaddr(*fpos - data_offset);
 	if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
 		tsz = buflen;
-		
-	while (buflen) {
-		struct kcore_list *m;
 
-		read_lock(&kclist_lock);
-		list_for_each_entry(m, &kclist_head, list) {
-			if (start >= m->addr && start < (m->addr+m->size))
-				break;
+	m = NULL;
+	while (buflen) {
+		/*
+		 * If this is the first iteration or the address is not within
+		 * the previous entry, search for a matching entry.
+		 */
+		if (!m || start < m->addr || start >= m->addr + m->size) {
+			list_for_each_entry(m, &kclist_head, list) {
+				if (start >= m->addr &&
+				    start < m->addr + m->size)
+					break;
+			}
 		}
-		read_unlock(&kclist_lock);
 
 		if (&m->list == &kclist_head) {
-			if (clear_user(buffer, tsz))
-				return -EFAULT;
+			if (clear_user(buffer, tsz)) {
+				ret = -EFAULT;
+				goto out;
+			}
 		} else if (m->type == KCORE_VMALLOC) {
 			vread(buf, (char *)start, tsz);
 			/* we have to zero-fill user buffer even if no read */
-			if (copy_to_user(buffer, buf, tsz))
-				return -EFAULT;
+			if (copy_to_user(buffer, buf, tsz)) {
+				ret = -EFAULT;
+				goto out;
+			}
 		} else if (m->type == KCORE_USER) {
 			/* User page is handled prior to normal kernel page: */
-			if (copy_to_user(buffer, (char *)start, tsz))
-				return -EFAULT;
+			if (copy_to_user(buffer, (char *)start, tsz)) {
+				ret = -EFAULT;
+				goto out;
+			}
 		} else {
 			if (kern_addr_valid(start)) {
 				/*
@@ -530,29 +484,37 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 				 * hardened user copy kernel text checks.
 				 */
 				if (probe_kernel_read(buf, (void *) start, tsz)) {
-					if (clear_user(buffer, tsz))
-						return -EFAULT;
+					if (clear_user(buffer, tsz)) {
+						ret = -EFAULT;
+						goto out;
+					}
 				} else {
-					if (copy_to_user(buffer, buf, tsz))
-						return -EFAULT;
+					if (copy_to_user(buffer, buf, tsz)) {
+						ret = -EFAULT;
+						goto out;
+					}
 				}
 			} else {
-				if (clear_user(buffer, tsz))
-					return -EFAULT;
+				if (clear_user(buffer, tsz)) {
+					ret = -EFAULT;
+					goto out;
+				}
 			}
 		}
 		buflen -= tsz;
 		*fpos += tsz;
 		buffer += tsz;
-		acc += tsz;
 		start += tsz;
 		tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
 	}
 
-	return acc;
+out:
+	up_read(&kclist_lock);
+	if (ret)
+		return ret;
+	return orig_buflen - buflen;
 }
 
-
 static int open_kcore(struct inode *inode, struct file *filp)
 {
 	if (!capable(CAP_SYS_RAWIO))
@@ -592,9 +554,8 @@ static int __meminit kcore_callback(struct notifier_block *self,
 	switch (action) {
 	case MEM_ONLINE:
 	case MEM_OFFLINE:
-		write_lock(&kclist_lock);
 		kcore_need_update = 1;
-		write_unlock(&kclist_lock);
+		break;
 	}
 	return NOTIFY_OK;
 }