From 5911eff83efedce91b856b54ae11d94692c7d71e Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Tue, 27 Mar 2012 10:02:59 -0700 Subject: [PATCH] chmod: fix symlink race condition * NEWS: Document this. * src/chmod.c (process_file): Don't follow symlink if we think the file is not a symlink. --- NEWS | 6 ++++++ src/chmod.c | 10 +++++++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/NEWS b/NEWS index c8d2bbcf07..40dadc27d4 100644 --- a/NEWS +++ b/NEWS @@ -2,6 +2,12 @@ GNU coreutils NEWS -*- outline -*- * Noteworthy changes in release ?.? (????-??-??) [?] +** Bug fixes + + When recursing, chmod -R no longer gets confused into following a symlink + if some other process simultaneously replaces a non-symlink with a symlink. + The fix is effective on modern hosts with the fchmodat or lchmod syscalls. + [bug introduced in the beginning] * Noteworthy changes in release 8.16 (2012-03-26) [stable] diff --git a/src/chmod.c b/src/chmod.c index aa4ac771c7..2e1f1c70b6 100644 --- a/src/chmod.c +++ b/src/chmod.c @@ -268,7 +268,15 @@ process_file (FTS *fts, FTSENT *ent) if (! S_ISLNK (old_mode)) { - if (chmodat (fts->fts_cwd_fd, file, new_mode) == 0) + /* Use any native support for AT_SYMLINK_NOFOLLOW, to avoid + following a symlink if there is a race. */ + #if HAVE_FCHMODAT || HAVE_LCHMOD + int follow_flag = AT_SYMLINK_NOFOLLOW; + #else + int follow_flag = 0; + #endif + + if (fchmodat (fts->fts_cwd_fd, file, new_mode, follow_flag) == 0) chmod_succeeded = true; else { -- 2.47.2