1 files changed, 61 insertions, 1 deletions

diff --git a/util-linux/mount.c b/util-linux/mount.c
index b92e2c297..19ac13930 100644
--- a/util-linux/mount.c
+++ b/util-linux/mount.c
@@ -1886,6 +1886,58 @@ static int nfsmount(struct mntent *mp, unsigned long vfsflags, char *filteropts)
 
 #endif // !ENABLE_FEATURE_MOUNT_NFS
 
+// Find "...,NAME=NUM,..." in the option string, remove "NAME=NUM" option
+// and return NUM.
+// Return 0 if not found.
+// All instances must be parsed and removed (for example, since kernel 5.4
+//      squashfs: Unknown parameter 'sizelimit'
+// will result if loopback mount option "sizelimit=NNN" is not removed
+// and squashfs sees it in option string).
+static unsigned long long cut_out_ull_opt(char *opts, const char *name_eq)
+{
+        unsigned long long ret = 0;
+
+        if (!opts) // allow NULL opts (simplifies callers' work)
+                return ret;
+
+        for (;;) {
+                char *end;
+                char *opt;
+
+                // Find comma-delimited "NAME="
+                for (;;) {
+                        opt = strstr(opts, name_eq);
+                        if (!opt)
+                                return ret;
+                        if (opt == opts)
+                                break; // found it (it's first opt)
+                        if (opt[-1] == ',') {
+                                opts = opt - 1;
+                                break; // found it (it's not a first opt)
+                        }
+                        // False positive like "VNAME=", we are at "N".
+                        // - skip it, loop back to searching
+                        opts = opt + 1;
+                }
+
+                ret = bb_strtoull(opt + strlen(name_eq), &end, 0);
+                if (errno && errno != EINVAL) {
+ err:
+                        bb_error_msg_and_die("bad option '%s'", opt);
+                }
+                if (*end == '\0') {
+                        // It is "[,]NAME=NUM\0" - truncate it and return
+                        *opts = '\0';
+                        return ret;
+                }
+                if (*end != ',')
+                        goto err;
+                // We are at trailing comma
+                // Remove "NAME=NUM," and loop back to check for duplicate opts
+                overlapping_strcpy(opt, end + 1);
+        }
+}
+
 // Mount one directory.  Handles CIFS, NFS, loopback, autobind, and filesystem
 // type detection.  Returns 0 for success, nonzero for failure.
 // NB: mp->xxx fields may be trashed on exit
@@ -2029,9 +2081,16 @@ static int singlemount(struct mntent *mp, int ignore_busy)
         ) {
                 // Do we need to allocate a loopback device for it?
                 if (ENABLE_FEATURE_MOUNT_LOOP && S_ISREG(st.st_mode)) {
+                        unsigned long long offset;
+                        unsigned long long sizelimit;
+
                         loopFile = bb_simplify_path(mp->mnt_fsname);
                         mp->mnt_fsname = NULL; // will receive malloced loop dev name
 
+                        // Parse and remove loopback options
+                        offset = cut_out_ull_opt(filteropts, "offset=");
+                        sizelimit = cut_out_ull_opt(filteropts, "sizelimit=");
+
                         // mount always creates AUTOCLEARed loopdevs, so that umounting
                         // drops them without any code in the userspace.
                         // This happens since circa linux-2.6.25:
@@ -2040,7 +2099,8 @@ static int singlemount(struct mntent *mp, int ignore_busy)
                         // Subject: Allow auto-destruction of loop devices
                         loopfd = set_loop(&mp->mnt_fsname,
                                         loopFile,
-                                        0,
+                                        offset,
+                                        sizelimit,
                                         ((vfsflags & MS_RDONLY) ? BB_LO_FLAGS_READ_ONLY : 0)
                                                 | BB_LO_FLAGS_AUTOCLEAR
                         );