From: Chris Down <chris@chrisdown.name>
Date: Thu, 22 Jan 2026 10:15:33 +0000 (+0800)
Subject: blockdev-util: Iterate through all DM layers
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F40426%2Fhead;p=thirdparty%2Fsystemd.git

blockdev-util: Iterate through all DM layers

get_block_device_harder_fd() currently only traverses one level of
device mapper stacking when looking for the underlying block device.
This causes issues with nested DM setups like dm-crypt on top of
dm-integrity, where we don't traverse enough to get the actual physical
device.

Fix this by iterating through all DM layers until we reach a device with
no underlying device.

Fixes: #40419
---

diff --git a/src/shared/blockdev-util.c b/src/shared/blockdev-util.c
index b138455acc9..44feae5ab60 100644
--- a/src/shared/blockdev-util.c
+++ b/src/shared/blockdev-util.c
@@ -346,14 +346,14 @@ int get_block_device_harder_fd(int fd, dev_t *ret) {
         assert(fd >= 0);
         assert(ret);
 
-        /* Gets the backing block device for a file system, and handles LUKS encrypted file systems, looking for its
-         * immediate parent, if there is one. */
+        /* Gets the backing block device for a file system, and handles LUKS encrypted file systems, looking
+         * for its underlying physical device, if there is one. */
 
         r = get_block_device_fd(fd, ret);
         if (r <= 0)
                 return r;
 
-        r = block_get_originating(*ret, ret, /* recursive= */ false);
+        r = block_get_originating(*ret, ret, /* recursive= */ true);
         if (r < 0)
                 log_debug_errno(r, "Failed to chase block device, ignoring: %m");