87 lines
2.7 KiB
Diff
87 lines
2.7 KiB
Diff
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From 5624e803c89ee79afe7c6fd0ef9929110505a800 Mon Sep 17 00:00:00 2001
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From: Peter Vicman <peter.vicman@gmail.com>
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Date: Fri, 20 Sep 2019 18:58:30 +0200
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Subject: [PATCH] add MS_BIND option when remouting bind mount
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when remounting bind mount add explicit MS_BIND to parameters
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to "hide" bind mount from user's view
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bind mount is only visible from /proc/self/mountinfo that's
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why we traverse the lines and using last entry in case
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multiple sources are mount over same mount point
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Signed-off-by: Peter Vicman <peter.vicman@gmail.com>
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---
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util-linux/mount.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
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1 file changed, 48 insertions(+)
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diff --git a/util-linux/mount.c b/util-linux/mount.c
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index 84c85c0..bc3fbda 100644
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--- a/util-linux/mount.c
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+++ b/util-linux/mount.c
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@@ -1887,6 +1887,50 @@ static int nfsmount(struct mntent *mp, unsigned long vfsflags, char *filteropts)
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#endif // !ENABLE_FEATURE_MOUNT_NFS
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+// Check mount point in /proc/self/mountinfo and identify bind mount
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+// return 1 for bind mount, 0 for normal mount
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+static int check_bind_mount(struct mntent *mp)
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+{
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+int mnt_dir_len;
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+char *p;
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+FILE *fp;
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+char *line = NULL;
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+int ret = 0;
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+
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+ // https://www.kernel.org/doc/Documentation/filesystems/proc.txt
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+ // 21 20 179:20 /coreelec_flash /flash ro,noatime shared:2 - ext4 /dev/data rw,resgid=1065,data=ordered
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+ // 20 22 179:1 / /flash ro,noatime shared:2 - vfat /dev/mmcblk1p1 ro,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro
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+
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+ fp = fopen("/proc/self/mountinfo", "r");
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+ if (fp == NULL)
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+ return ret;
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+
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+ // remove trailing slash
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+ mnt_dir_len = strlen(mp->mnt_dir);
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+ if (mnt_dir_len > 1 && mp->mnt_dir[mnt_dir_len - 1] == '/') {
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+ mnt_dir_len--;
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+ mp->mnt_dir[mnt_dir_len] = '\0';
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+ }
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+
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+ while ((line = xmalloc_fgetline(fp)) != NULL) {
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+ // find mount point
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+ p = strstr(line, mp->mnt_dir);
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+ if (p == NULL)
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+ continue;
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+
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+ // bind mount has folder for root and not just "/"
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+ ret = 0; // always use result from last entry
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+ if (strncmp(p - 2, "/ ", 2) != 0)
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+ ret = 1;
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+ }
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+
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+ if (line != NULL)
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+ free(line);
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+
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+ fclose(fp);
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+ return ret;
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+}
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+
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// Mount one directory. Handles CIFS, NFS, loopback, autobind, and filesystem
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// type detection. Returns 0 for success, nonzero for failure.
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// NB: mp->xxx fields may be trashed on exit
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@@ -2058,6 +2102,10 @@ static int singlemount(struct mntent *mp, int ignore_busy)
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vfsflags |= MS_BIND;
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}
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+ // add explicit MS_BIND if remounting bind mount
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+ if ((vfsflags & MS_REMOUNT) && (check_bind_mount(mp) == 1))
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+ vfsflags |= MS_BIND;
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+
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// If we know the fstype (or don't need to), jump straight
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// to the actual mount.
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if (mp->mnt_type || (vfsflags & (MS_REMOUNT | MS_BIND | MS_MOVE))) {
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--
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2.7.4
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