From 7fec10b7f41fa32e71aa6377bd04cd7c6fb419e0 Mon Sep 17 00:00:00 2001 From: Junio C Hamano Date: Fri, 18 Jan 2008 23:42:00 -0800 Subject: [PATCH] index: be careful when handling long names We currently use lower 12-bit (masked with CE_NAMEMASK) in the ce_flags field to store the length of the name in cache_entry, without checking the length parameter given to create_ce_flags(). This can make us store incorrect length. Currently we are mostly protected by the fact that many codepaths first copy the path in a variable of size PATH_MAX, which typically is 4096 that happens to match the limit, but that feels like a bug waiting to happen. Besides, that would not allow us to shorten the width of CE_NAMEMASK to use the bits for new flags. This redefines the meaning of the name length stored in the cache_entry. A name that does not fit is represented by storing CE_NAMEMASK in the field, and the actual length needs to be computed by actually counting the bytes in the name[] field. This way, only the unusually long paths need to suffer. Signed-off-by: Junio C Hamano Signed-off-by: Linus Torvalds --- cache.h | 17 +++++++++++++++-- read-cache.c | 12 +++++++++++- t/t0000-basic.sh | 20 ++++++++++++++++++++ 3 files changed, 46 insertions(+), 3 deletions(-) diff --git a/cache.h b/cache.h index 4a054c540..9eaffdefd 100644 --- a/cache.h +++ b/cache.h @@ -131,8 +131,21 @@ struct cache_entry { #define CE_UPDATE (0x10000) #define CE_REMOVE (0x20000) -#define create_ce_flags(len, stage) ((len) | ((stage) << CE_STAGESHIFT)) -#define ce_namelen(ce) (CE_NAMEMASK & (ce)->ce_flags) +static inline unsigned create_ce_flags(size_t len, unsigned stage) +{ + if (len >= CE_NAMEMASK) + len = CE_NAMEMASK; + return (len | (stage << CE_STAGESHIFT)); +} + +static inline size_t ce_namelen(const struct cache_entry *ce) +{ + size_t len = ce->ce_flags & CE_NAMEMASK; + if (len < CE_NAMEMASK) + return len; + return strlen(ce->name + CE_NAMEMASK) + CE_NAMEMASK; +} + #define ce_size(ce) cache_entry_size(ce_namelen(ce)) #define ondisk_ce_size(ce) ondisk_cache_entry_size(ce_namelen(ce)) #define ce_stage(ce) ((CE_STAGEMASK & (ce)->ce_flags) >> CE_STAGESHIFT) diff --git a/read-cache.c b/read-cache.c index 82a6238b7..528f697f5 100644 --- a/read-cache.c +++ b/read-cache.c @@ -928,6 +928,8 @@ int read_index(struct index_state *istate) static void convert_from_disk(struct ondisk_cache_entry *ondisk, struct cache_entry *ce) { + size_t len; + ce->ce_ctime = ntohl(ondisk->ctime.sec); ce->ce_mtime = ntohl(ondisk->mtime.sec); ce->ce_dev = ntohl(ondisk->dev); @@ -939,7 +941,15 @@ static void convert_from_disk(struct ondisk_cache_entry *ondisk, struct cache_en /* On-disk flags are just 16 bits */ ce->ce_flags = ntohs(ondisk->flags); hashcpy(ce->sha1, ondisk->sha1); - memcpy(ce->name, ondisk->name, ce_namelen(ce)+1); + + len = ce->ce_flags & CE_NAMEMASK; + if (len == CE_NAMEMASK) + len = strlen(ondisk->name); + /* + * NEEDSWORK: If the original index is crafted, this copy could + * go unchecked. + */ + memcpy(ce->name, ondisk->name, len + 1); } /* remember to discard_cache() before reading a different cache! */ diff --git a/t/t0000-basic.sh b/t/t0000-basic.sh index 4e49d5906..9f84b8d3a 100755 --- a/t/t0000-basic.sh +++ b/t/t0000-basic.sh @@ -297,4 +297,24 @@ test_expect_success 'absolute path works as expected' ' test "$sym" = "$(test-absolute-path $dir2/syml)" ' +test_expect_success 'very long name in the index handled sanely' ' + + a=a && # 1 + a=$a$a$a$a$a$a$a$a$a$a$a$a$a$a$a$a && # 16 + a=$a$a$a$a$a$a$a$a$a$a$a$a$a$a$a$a && # 256 + a=$a$a$a$a$a$a$a$a$a$a$a$a$a$a$a$a && # 4096 + a=${a}q && + + >path4 && + git update-index --add path4 && + ( + git ls-files -s path4 | + sed -e "s/ .*/ /" | + tr -d "\012" + echo "$a" + ) | git update-index --index-info && + len=$(git ls-files "a*" | wc -c) && + test $len = 4098 +' + test_done -- 2.30.2