From 0d19fcf6c24f7dcf585ad3423518068b5789f3b0 Mon Sep 17 00:00:00 2001 From: "Yann E. MORIN" Date: Tue, 3 Apr 2018 20:54:56 +0200 Subject: [PATCH] core/download: fix when the BR2_DL_DIR does not accept hardlinks When the BR2_DL_DIR is a mountpoint (presumably shared between various machine, or mounted from the local host when running in a VM), it is possible that it does not support hardlinks (e.g. samba, or the VMWare VMFS, etc...). If the hardlink fails, fallback to copying the file. As a last resort, if that also fails, eventually fallback to doing the download. Note: this means that the dl-wrapper is no longer atomic-safe: the code suffers of a TOCTTOU condition: the file may be created in-between the check and the moment we try to ln/cp it. Fortunately, the dl-wrapper is now run under an flock, so we're still safe. If we eventually go for a more fine-grained implementation, we'll have to be careful then. Reported-by: Arnout Vandecappelle Signed-off-by: "Yann E. MORIN" Cc: Arnout Vandecappelle Cc: Peter Korsgaard Cc: Maxime Hadjinlian Signed-off-by: Peter Korsgaard --- support/download/dl-wrapper | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/support/download/dl-wrapper b/support/download/dl-wrapper index ce44752df0..38430738eb 100755 --- a/support/download/dl-wrapper +++ b/support/download/dl-wrapper @@ -56,8 +56,13 @@ main() { # Legacy handling: check if the file already exists in the global # download directory. If it does, hard-link it. If it turns out it # was an incorrect download, we'd still check it below anyway. + # If we can neither link nor copy, fallback to doing a download. + # NOTE! This is not atomic, is subject to TOCTTOU, but the whole + # dl-wrapper runs under an flock, so we're safe. if [ ! -e "${output}" -a -e "${old_dl_dir}/${filename}" ]; then - ln "${old_dl_dir}/${filename}" "${output}" + ln "${old_dl_dir}/${filename}" "${output}" || \ + cp "${old_dl_dir}/${filename}" "${output}" || \ + true fi # If the output file already exists and: