From: Craig Small <csmall@dropbear.xyz>
Date: Tue, 27 Oct 2020 10:59:25 +0000 (+1100)
Subject: fuser: Check pathname only on non-block devices
X-Git-Tag: v23.4rc1~9
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=b4566f854f29cad3d2249abcb7e472f5d3fbf169;p=psmisc

fuser: Check pathname only on non-block devices

The referenced commit we would check the pathname to
ensure it matched our target. This worked fine for
real files. However for block devices it would fail
because "/dev/sda1" doesn't match "/mnt/myfile".

We only check the pathname if the thing we are matching
against is not a block file.

Thanks to @MarsChan for the report and also the suggested
fix!

References:
 commit 5c979b38253d187a8ecb8e52a0878b8bb668894f
 psmisc/psmisc#31

Signed-off-by: Craig Small <csmall@dropbear.xyz>
---

diff --git a/ChangeLog b/ChangeLog
index 1a88488..3e77df6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,7 @@ Changes in NEXT
 ===============
 	* pstree: Do not crash on missing processes !21
 	* fuser: Get less confused about duplicate dev_id !10
+	* fuser: Only check pathname on non-block devices !31
 
 Changes in 23.3
 ===============
diff --git a/src/fuser.c b/src/fuser.c
index 70da121..03e6237 100644
--- a/src/fuser.c
+++ b/src/fuser.c
@@ -1606,13 +1606,15 @@ check_dir(const pid_t pid, const char *dirname, struct device_list *dev_head,
 				if (thedev != dev_tmp->device)
 					continue;
 
-				/* check the paths match */
-				if (readlink(filepath, real_filepath, PATH_MAX-1) < 0) {
-				    if (strncmp(dev_tmp->name->filename, filepath, strlen(dev_tmp->name->filename)) != 0)
-					continue;
-				} else {
-				    if (strncmp(dev_tmp->name->filename, real_filepath, strlen(dev_tmp->name->filename)) != 0)
-					continue;
+				/* check the paths match if it is not a block device */
+				if (! S_ISBLK(dev_tmp->name->st.st_mode)) {
+				    if (readlink(filepath, real_filepath, PATH_MAX-1) < 0) {
+					if (strncmp(dev_tmp->name->filename, filepath, strlen(dev_tmp->name->filename)) != 0)
+					    continue;
+				    } else {
+					if (strncmp(dev_tmp->name->filename, real_filepath, strlen(dev_tmp->name->filename)) != 0)
+					    continue;
+				    }
 				}
 				if (access == ACCESS_FILE
 				    && (lstat(filepath, &lst) == 0)