From c96e7736d85e40685939011e6d51b3c0a28739a3 Mon Sep 17 00:00:00 2001 From: Vivek Goyal Date: Wed, 18 Jul 2012 09:33:51 -0400 Subject: [PATCH] vmcore-dmesg: Do not write beyond end of buffer scan_vmcoreinfo() currently assumes that every vmcoreinfo note line ends with \n and overwrites new line with \0. But last entry in note, CRASHTIME= does not end with \n and this leads to corrupting memory as we write beyond end of buffer. Normally things were fine but when I added some fields to vmcoreinfo, this bug started showing and vmcore-dmesg started crashing. I am planning to send a patch to fix this in kernel but it might be good idea to handle this case in user space too so that vmcore-dmesg works fine with cores of older kernels. Signed-off-by: Vivek Goyal Signed-off-by: Simon Horman --- vmcore-dmesg/vmcore-dmesg.c | 29 ++++++++++++++++++++++++++++- 1 files changed, 28 insertions(+), 1 deletions(-) diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c index 8518150..2e692de 100644 --- a/vmcore-dmesg/vmcore-dmesg.c +++ b/vmcore-dmesg/vmcore-dmesg.c @@ -14,6 +14,7 @@ #include #include #include +#include /* The 32bit and 64bit note headers make it clear we don't care */ typedef Elf32_Nhdr Elf_Nhdr; @@ -220,6 +221,9 @@ static void scan_vmcoreinfo(char *start, size_t size) { char *last = start + size - 1; char *pos, *eol; + char temp_buf[1024]; + bool last_line = false; + #define SYMBOL(sym) { \ .str = "SYMBOL(" #sym ")=", \ .name = #sym, \ @@ -243,7 +247,27 @@ static void scan_vmcoreinfo(char *start, size_t size) /* Find the end of the current line */ for (eol = pos; (eol <= last) && (*eol != '\n') ; eol++) ; - len = eol - pos + 1; + if (eol > last) { + /* + * We did not find \n and note ended. Currently kernel + * is appending last field CRASH_TIME without \n. It + * is ugly but handle it. + */ + eol = last; + len = eol - pos + 1; + if (len >= sizeof(temp_buf)) + len = sizeof(temp_buf) - 1; + strncpy(temp_buf, pos, len); + temp_buf[len + 1] = '\0'; + + pos = temp_buf; + len = len + 1; + eol = pos + len -1; + last_line = true; + } else { + len = eol - pos + 1; + } + /* Stomp the last character so I am guaranteed a terminating null */ *eol = '\0'; /* Copy OSRELEASE if I see it */ @@ -266,6 +290,9 @@ static void scan_vmcoreinfo(char *start, size_t size) /* Remember the virtual address */ *symbol[i].vaddr = vaddr; } + + if (last_line) + break; } } -- 1.7.1