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mount: "mount -o rw ...." should not fall back to RO mount

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The reported case was an attempt to remount,rw a CD-ROM:

  mount -o remount,rw /mnt/sr0

which "succeeded" by falling back to RO:

  mount("/dev/sr0", "/mnt/sr0", 0x412862, MS_REMOUNT|MS_SILENT|MS_RELATIME, "nojoliet,check=s,map=n,blocksize"...) = -1 EROFS (Read-only file system)
  ...
  mount("/dev/sr0", "/mnt/sr0", 0x412862, MS_RDONLY|MS_REMOUNT|MS_SILENT|MS_RELATIME, "nojoliet,check=s,map=n,blocksize"...) = 0

Clearly, not what was intended!

function                                             old     new   delta
parse_mount_options                                  241     267     +26
mount_main                                          1198    1211     +13
singlemount                                         1301    1313     +12
inetd_main                                          1919    1911      -8
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/1 up/down: 51/-8)              Total: 43 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2021-10-08 02:16:41 +02:00
parent c28313bb17
commit cf4dc4a09d
1 changed files with 13 additions and 8 deletions
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21
util-linux/mount.c
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@ -589,7 +589,7 @@ static void append_mount_options(char **oldopts, const char *newopts)
// Use the mount_options list to parse options into flags.
// Also update list of unrecognized options if unrecognized != NULL
static unsigned long parse_mount_options(char *options, char **unrecognized)
static unsigned long parse_mount_options(char *options, char **unrecognized, uint32_t *opt)
{
unsigned long flags = MS_SILENT;
@ -617,6 +617,11 @@ static unsigned long parse_mount_options(char *options, char **unrecognized)
flags &= fl;
else
flags |= fl;
/* If we see "-o rw" on command line, it's the same as -w:
* "do not try to fall back to RO mounts"
*/
if (fl == ~MS_RDONLY && opt)
(*opt) |= OPT_w;
goto found;
}
option_str += opt_len + 1;
@ -1973,7 +1978,7 @@ static int singlemount(struct mntent *mp, int ignore_busy)
errno = 0;
vfsflags = parse_mount_options(mp->mnt_opts, &filteropts);
vfsflags = parse_mount_options(mp->mnt_opts, &filteropts, NULL);
// Treat fstype "auto" as unspecified
if (mp->mnt_type && strcmp(mp->mnt_type, "auto") == 0)
@ -2047,7 +2052,7 @@ static int singlemount(struct mntent *mp, int ignore_busy)
len, share,
share + len + 1 /* "dir1/dir2" */
);
parse_mount_options(unc, &filteropts);
parse_mount_options(unc, &filteropts, NULL);
if (ENABLE_FEATURE_CLEAN_UP) free(unc);
}
@ -2073,7 +2078,7 @@ static int singlemount(struct mntent *mp, int ignore_busy)
// (instead of _numeric_ iface_id) with glibc.
// This probably should be fixed in glibc, not here.
// The workaround is to manually specify correct "ip=ADDR%n" option.
parse_mount_options(ip, &filteropts);
parse_mount_options(ip, &filteropts, NULL);
if (ENABLE_FEATURE_CLEAN_UP) free(ip);
}
@ -2355,7 +2360,7 @@ int mount_main(int argc UNUSED_PARAM, char **argv)
// Past this point, we are handling either "mount -a [opts]"
// or "mount [opts] single_param"
cmdopt_flags = parse_mount_options(cmdopts, NULL);
cmdopt_flags = parse_mount_options(cmdopts, NULL, &option_mask32);
if (nonroot && (cmdopt_flags & ~MS_SILENT)) // Non-root users cannot specify flags
bb_simple_error_msg_and_die(bb_msg_you_must_be_root);
@ -2429,7 +2434,7 @@ int mount_main(int argc UNUSED_PARAM, char **argv)
continue;
// Skip noauto and swap anyway
if ((parse_mount_options(mtcur->mnt_opts, NULL) & (MOUNT_NOAUTO | MOUNT_SWAP))
if ((parse_mount_options(mtcur->mnt_opts, NULL, NULL) & (MOUNT_NOAUTO | MOUNT_SWAP))
// swap is bogus "fstype", parse_mount_options can't check fstypes
|| strcasecmp(mtcur->mnt_type, "swap") == 0
) {
@ -2490,7 +2495,7 @@ int mount_main(int argc UNUSED_PARAM, char **argv)
// exit_group(32) = ?
#if 0
// In case we want to simply skip swap partitions:
l = parse_mount_options(mtcur->mnt_opts, NULL);
l = parse_mount_options(mtcur->mnt_opts, NULL, NULL);
if ((l & MOUNT_SWAP)
// swap is bogus "fstype", parse_mount_options can't check fstypes
|| strcasecmp(mtcur->mnt_type, "swap") == 0
@ -2500,7 +2505,7 @@ int mount_main(int argc UNUSED_PARAM, char **argv)
#endif
if (nonroot) {
// fstab must have "users" or "user"
l = parse_mount_options(mtcur->mnt_opts, NULL);
l = parse_mount_options(mtcur->mnt_opts, NULL, NULL);
if (!(l & MOUNT_USERS))
bb_simple_error_msg_and_die(bb_msg_you_must_be_root);
}