From cf606e3ddd8666b990a6560be77eb9f28af0e47d Mon Sep 17 00:00:00 2001 From: Andy Whitcroft Date: Tue, 15 May 2007 17:33:25 +0100 Subject: [PATCH] git name-rev writes beyond the end of malloc() with large generations When using git name-rev on my kernel tree I triggered a malloc() corruption warning from glibc. apw@pinky$ git log --pretty=one $N/base.. | git name-rev --stdin *** glibc detected *** malloc(): memory corruption: 0x0bff8950 *** Aborted This comes from name_rev() which is building the name of the revision in a malloc'd string, which it sprintf's into: char *new_name = xmalloc(len + 8); [...] sprintf(new_name, "%.*s~%d^%d", len, tip_name, generation, parent_number); This allocation is only sufficient if the generation number is less than 5 digits, in my case generation was 13432. In reality parent_number can be up to 16 so that also can require two digits, reducing us to 3 digits before we are at risk of blowing this allocation. This patch introduces a decimal_length() which approximates the number of digits a type may hold, it produces the following: Type Longest Value Len Est ---- ------------- --- --- unsigned char 256 3 4 unsigned short 65536 5 6 unsigned long 4294967296 10 11 unsigned long long 18446744073709551616 20 21 char -128 4 4 short -32768 6 6 long -2147483648 11 11 long long -9223372036854775808 20 21 This is then used to size the new_name. Signed-off-by: Andy Whitcroft Signed-off-by: Junio C Hamano --- builtin-name-rev.c | 5 ++++- git-compat-util.h | 3 +++ 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/builtin-name-rev.c b/builtin-name-rev.c index c02222436..ef1638590 100644 --- a/builtin-name-rev.c +++ b/builtin-name-rev.c @@ -58,7 +58,10 @@ copy_data: parents = parents->next, parent_number++) { if (parent_number > 1) { int len = strlen(tip_name); - char *new_name = xmalloc(len + 8); + char *new_name = xmalloc(len + + 1 + decimal_length(generation) + /* ~ */ + 1 + 2 + /* ^NN */ + 1); if (len > 2 && !strcmp(tip_name + len - 2, "^0")) len -= 2; diff --git a/git-compat-util.h b/git-compat-util.h index bd93b6257..7ed8b88b1 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -13,6 +13,9 @@ #define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0])) +/* Approximation of the length of the decimal representation of this type. */ +#define decimal_length(x) ((int)(sizeof(x) * 2.56 + 0.5) + 1) + #if !defined(__APPLE__) && !defined(__FreeBSD__) #define _XOPEN_SOURCE 600 /* glibc2 and AIX 5.3L need 500, OpenBSD needs 600 for S_ISLNK() */ #define _XOPEN_SOURCE_EXTENDED 1 /* AIX 5.3L needs this */ -- 2.30.2