Re: [pacman-dev] [PATCH 5/7] fix off-by-one error in _alpm_filelist_resolve

On Thu, 14 Feb 2013 22:12:59 +1000 Allan McRae wrote:

On 14/02/13 09:54, Andrew Gregory wrote:

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Signed-off-by: Andrew Gregory ---

OK... I'm tired, so feel free to point out where I am wring here...

AFAIK, realpath will not return a trailing "/". So what is being fixed here? If I take out the unneeded if statement, if am failing to see the off-by-one error...

Realpath does include a "trailing" '/' when root == "/". That's why this was passing the test suite. You can see the error by building a package with a file in /lib and then updating it with the file in /usr/lib.

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lib/libalpm/filelist.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/lib/libalpm/filelist.c b/lib/libalpm/filelist.c index f29bb7c..c2ca1ca 100644 --- a/lib/libalpm/filelist.c +++ b/lib/libalpm/filelist.c @@ -198,12 +198,15 @@ int _alpm_filelist_resolve(alpm_handle_t *handle, alpm_filelist_t *files) if(realpath(handle->root, path) == NULL){ return -1; } - root_len = strlen(path) + 1; - if(root_len >= PATH_MAX) { + root_len = strlen(path); + if(root_len + 1 >= PATH_MAX) { return -1; } - path[root_len - 1] = '/'; - path[root_len] = '\0'; + if(path[root_len - 1] != '/') { + path[root_len] = '/'; + root_len++; + path[root_len] = '\0'; + }

ret = _alpm_filelist_resolve_link(files, &i, path, root_len, 0);