[PATCH v2 16/20] vmcore: check NT_VMCORE_PAD as a mark indicating the end of ELF note buffer

[d.hatayama@xxxxxxxxxxxxxx (HATAYAMA Daisuke)]

Modern kernel marks the end of ELF note buffer with NT_VMCORE_PAD type
note in order to make the buffer satisfy mmap()'s page-size boundary
requirement. This patch makes finishing reading each buffer if the
note type now being read is NT_VMCORE_PAD type.

Signed-off-by: HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com>
---

 fs/proc/vmcore.c |   24 ++++++++++++++++++++++++
 1 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index c8899dc..e432946 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -259,12 +259,24 @@ static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
 		}
 		nhdr_ptr = notes_section;
 		for (j = 0; j < max_sz; j += sz) {
+			char *name;
+
+			/* Old kernel marks the end of ELF note buffer
+			 * with empty header. */
 			if (nhdr_ptr->n_namesz == 0)
 				break;
 			sz = sizeof(Elf64_Nhdr) +
 				((nhdr_ptr->n_namesz + 3) & ~3) +
 				((nhdr_ptr->n_descsz + 3) & ~3);
 			real_sz += sz;
+
+			/* Modern kernel marks the end of ELF note
+			 * buffer with NT_VMCORE_PAD type note. */
+			name = (char *)(nhdr_ptr + 1);
+			if (strncmp(name, VMCOREINFO_NOTE_NAME,
+				    sizeof(VMCOREINFO_NOTE_NAME)) == 0
+			    && nhdr_ptr->n_type == NT_VMCORE_PAD)
+				break;
 			nhdr_ptr = (Elf64_Nhdr*)((char*)nhdr_ptr + sz);
 		}
 
@@ -369,12 +381,24 @@ static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
 		}
 		nhdr_ptr = notes_section;
 		for (j = 0; j < max_sz; j += sz) {
+			char *name;
+
+			/* Old kernel marks the end of ELF note buffer
+			 * with empty header. */
 			if (nhdr_ptr->n_namesz == 0)
 				break;
 			sz = sizeof(Elf32_Nhdr) +
 				((nhdr_ptr->n_namesz + 3) & ~3) +
 				((nhdr_ptr->n_descsz + 3) & ~3);
 			real_sz += sz;
+
+			/* Modern kernel marks the end of ELF note
+			 * buffer with NT_VMCORE_PAD type note. */
+			name = (char *)(nhdr_ptr + 1);
+			if (strncmp(name, VMCOREINFO_NOTE_NAME,
+				    sizeof(VMCOREINFO_NOTE_NAME)) == 0
+			    && nhdr_ptr->n_type == NT_VMCORE_PAD)
+				break;
 			nhdr_ptr = (Elf32_Nhdr*)((char*)nhdr_ptr + sz);
 		}