From dbfc83bdcab941ce04200f97879f2a79fd0f2a0b Mon Sep 17 00:00:00 2001 From: Qixing ksyx Xue Date: Thu, 25 May 2023 11:10:54 -0400 Subject: elf: Add test for locating libraries in root dir (bug 30435) When dlopen is being called, efforts have been made to improve future lookup performance. This includes marking a search path as non-existent using `stat`. However, if the root directory is given as a search path, there exists a bug which erroneously marks it as non-existing. The bug is reproduced under the following sequence: 1. dlopen is called to open a shared library, with at least: 1) a dependency 'A.so' not directly under the '/' directory (e.g. /lib/A.so), and 2) another dependency 'B.so' resides in '/'. 2. for this bug to reproduce, 'A.so' should be searched *before* 'B.so'. 3. it first tries to find 'A.so' in /, (e.g. /A.so): - this will (obviously) fail, - since it's the first time we have seen the '/' directory, its 'status' is 'unknown'. 4. `buf[buflen - namelen - 1] = '\0'` is executed: - it intends to remove the leaf and its final slash, - because of the speciality of '/', its buflen == namelen + 1, - it erroneously clears the entire buffer. 6. it then calls 'stat' with the empty buffer: - which will result in an error. 7. so it marks '/' as 'nonexisting', future lookups will not consider this path. 8. while /B.so *does* exist, failure to look it up in the '/' directory leads to a 'cannot open shared object file' error. This patch fixes the bug by preventing 'buflen', an index to put '\0', from being set to 0, so that the root '/' is always kept. Relative search paths are always considered as 'existing' so this wont be affected. Writeup by Moody Liu Suggested-by: Carlos O'Donell Signed-off-by: Qixing ksyx Xue Reviewed-by: Siddhesh Poyarekar --- elf/tst-rootdir.root/preclean.req | 0 1 file changed, 0 insertions(+), 0 deletions(-) create mode 100644 elf/tst-rootdir.root/preclean.req (limited to 'elf/tst-rootdir.root') diff --git a/elf/tst-rootdir.root/preclean.req b/elf/tst-rootdir.root/preclean.req new file mode 100644 index 0000000..e69de29 -- cgit v1.1