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* [pseudo][PATCH] pseudo_util: Fix resolving relative paths from "/"
@ 2022-08-24 16:51 Tomi Belan
  2022-08-24 20:39 ` [OE-core] " Luca Ceresoli
  0 siblings, 1 reply; 4+ messages in thread
From: Tomi Belan @ 2022-08-24 16:51 UTC (permalink / raw)
  To: openembedded-core; +Cc: Richard Purdie, Tomi Belan

pseudo_fix_path() incorrectly assumed that 'base' never ends with a slash
because it's a canonical path. However, base can be "/" - a path which is
canonical and yet starts with a slash. This happens when pseudo_cwd is "/" or
when we're starting from a dirfd pointing to "/". The wrong result from
pseudo_fix_path() caused the database lookup to fail and made pseudo abort.

Signed-off-by: Tomi Belan <tomi.belan@gmail.com>
---
Hi. Here is my third patch for 'pseudo'. I included a test that demonstrates
the fix. Try "make test" with old and new pseudo_util.c to see the difference.
Run it with PSEUDO_DEBUG to see what happens and how it leads to an abort.

JFYI: The real fix is to check "baselen == 1". The "rootlen == 1" condition is
just for symmetry. Unlike pseudo_cwd and fd_path(), which can be "/", I think
pseudo_chroot will never be "/" because pseudo_client_chroot sets it to NULL
instead. So rootlen should never be 1. It's just to be safe.

 pseudo_util.c                   | 12 +++++++++---
 test/test-relative-from-root.sh | 14 ++++++++++++++
 2 files changed, 23 insertions(+), 3 deletions(-)
 create mode 100755 test/test-relative-from-root.sh

diff --git a/pseudo_util.c b/pseudo_util.c
index e8e9803..64636b7 100644
--- a/pseudo_util.c
+++ b/pseudo_util.c
@@ -792,9 +792,9 @@ static char *pathbufs[PATHBUFS] = { 0 };
 static int pathbuf = 0;
 
 /* Canonicalize path.  "base", if present, is an already-canonicalized
- * path of baselen characters, presumed not to end in a /.  path is
- * the new path to be canonicalized.  The tricky part is that path may
- * contain symlinks, which must be resolved.
+ * path of baselen characters, presumed not to end in a / unless it is
+ * just "/".  path is the new path to be canonicalized.  The tricky part
+ * is that path may contain symlinks, which must be resolved.
  */
 char *
 pseudo_fix_path(const char *base, const char *path, size_t rootlen, size_t baselen, size_t *lenp, int leave_last) {
@@ -808,6 +808,12 @@ pseudo_fix_path(const char *base, const char *path, size_t rootlen, size_t basel
 		pseudo_diag("can't fix empty path.\n");
 		return 0;
 	}
+	if (baselen == 1) {
+		baselen = 0;
+	}
+	if (rootlen == 1) {
+		rootlen = 0;
+	}
 	newpathlen = pseudo_path_max();
 	pathlen = strlen(path);
 	/* Crazy shell code (e.g. libtool) can pass in a command pipeline as a path which exceeds the max path
diff --git a/test/test-relative-from-root.sh b/test/test-relative-from-root.sh
new file mode 100755
index 0000000..e2c230e
--- /dev/null
+++ b/test/test-relative-from-root.sh
@@ -0,0 +1,14 @@
+#!/bin/bash
+# pseudo had a bug that made it abort() when looking up a relative path from
+# base "/", such as by openat(dirfd_of_root, "foo/bar") or when cwd is /. It
+# tried to look up base+"/"+path = "//foo/bar", which is wrong.
+
+set -e
+
+touch f1
+relative_pwd=${PWD#/}
+
+cd /
+cat "$relative_pwd/f1"
+
+rm "$relative_pwd/f1"
-- 
2.25.1



^ permalink raw reply related	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-08-26 13:30 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-08-24 16:51 [pseudo][PATCH] pseudo_util: Fix resolving relative paths from "/" Tomi Belan
2022-08-24 20:39 ` [OE-core] " Luca Ceresoli
2022-08-24 21:09   ` Tomi Belan
2022-08-26 13:30     ` Luca Ceresoli

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