From cf4dc4a09d2a7516e00c276396da85e1088a0ddf Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Fri, 8 Oct 2021 02:16:41 +0200 Subject: [PATCH] mount: "mount -o rw ...." should not fall back to RO mount 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 --- util-linux/mount.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/util-linux/mount.c b/util-linux/mount.c index 44afdbcff..4e65b6b46 100644 --- a/util-linux/mount.c +++ b/util-linux/mount.c @@ -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); }