The directory that readdir() and closedir() work on is BUS_PATH ("/sys/bus/virtio/drivers/9pnet_virtio"), not "/sys/block". Fix the error messages that are sent when readdir() or closedir() fails. (The invalid "sys/block" pathname could be a leftover from when the directory reading logic was (perhaps) copied from "daemon/sync.c".) Fixes: 5f10c3350338bbca735a74db26f98da968957bd9 Signed-off-by: Laszlo Ersek <lersek(a)redhat.com&gt; Acked-by: Richard W.M. Jones <rjones(a)redhat.com&gt; --- Notes: v3: - pick up Rich's ACK v2: - new patch: unrelated fix for a wart I'd come across while working the BZ daemon/9p.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/daemon/9p.c b/daemon/9p.c index 743a96abd449..9a3a5cfdf274 100644 --- a/daemon/9p.c +++ b/daemon/9p.c @@ -106,14 +106,14 @@ do_list_9p (void) /* Check readdir didn't fail */ if (errno != 0) { - reply_with_perror ("readdir: /sys/block"); + reply_with_perror ("readdir: " BUS_PATH); closedir (dir); return NULL; } /* Close the directory handle */ if (closedir (dir) == -1) { - reply_with_perror ("closedir: /sys/block"); + reply_with_perror ("closedir: " BUS_PATH); return NULL; } -- 2.19.1.3.g30247aa5d201

"parted" incorrectly reports "loop" rather than "msdos" for the partition table type, when the (fake) partition table comes from the "--mbr" option of "mkfs.fat" (in dosfstools-4.2+), and the FAT variant in question is FAT16 or FAT32. (See RHBZ#2026224.) Work this around by - parsing the partition table ourselves, and - overriding "loop" with "msdos" when appropriate. Note that when the FAT variant is FAT12, "parted" fails to parse the fake MBR partition table completely (see RHBZ#2026220), which we cannot work around. However, FAT12 should be a rare corner case in libguestfs usage -- "mkfs.fat" auto-chooses FAT12 only below 9MB disk size, and even "-F 12" can only be forced up to and including 255MB disk size. Add the helper function "has_bogus_mbr" to the Utils module; we'll use it elsewhere too. Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1931821 Signed-off-by: Laszlo Ersek <lersek(a)redhat.com&gt; Acked-by: Richard W.M. Jones <rjones(a)redhat.com&gt; --- Notes: v3: - pick up Rich's ACK - drop "Unix." namespace selector from "read" [Rich] - factor "Bytes.get_uint8 sec0" out to "sec0at" [Rich, Laszlo] v2: - new patch (the hard one) daemon/utils.mli | 10 ++++++++++ daemon/parted.ml | 7 ++++++- daemon/utils.ml | 45 +++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 61 insertions(+), 1 deletion(-) diff --git a/daemon/utils.mli b/daemon/utils.mli index ec1127f7211e..d7b7aeba0657 100644 --- a/daemon/utils.mli +++ b/daemon/utils.mli @@ -56,6 +56,16 @@ val sort_device_names : string list -> string list This also deals with partition numbers, and works whether or not [/dev/] is present. *) +val has_bogus_mbr : string -> bool +(** Check whether the first sector of the device contains a bogus MBR partition + table; namely one where the first partition table entry describes a + partition that starts at absolute sector 0, thereby overlapping the + partition table itself. + + dosfstools-4.2+ creates bogus partition tables like this by default when + formatting non-removable, non-partitioned block devices. Refer to + RHBZ#1931821. *) + val proc_unmangle_path : string -> string (** Reverse kernel path escaping done in fs/seq_file.c:mangle_path. This is inconsistently used for /proc fields. *) diff --git a/daemon/parted.ml b/daemon/parted.ml index 29b98c4806c1..53077d91afdd 100644 --- a/daemon/parted.ml +++ b/daemon/parted.ml @@ -118,7 +118,12 @@ let part_get_parttype device = let fields = String.nsplit ":" device_line in match fields with | _::_::_::_::_::"loop"::_ -> (* If "loop" return an error (RHBZ#634246). *) - failwithf "%s: not a partitioned device" device + (* ... Unless parted failed to recognize the fake MBR that mkfs.fat from + * dosfstools-4.2+ created. In that case, return "msdos" for MBR + * (RHBZ#1931821). + *) + if Utils.has_bogus_mbr device then "msdos" + else failwithf "%s: not a partitioned device" device | _::_::_::_::_::ret::_ -> ret | _ -> failwithf "%s: cannot parse the output of parted" device diff --git a/daemon/utils.ml b/daemon/utils.ml index b56306055634..c51a0d181365 100644 --- a/daemon/utils.ml +++ b/daemon/utils.ml @@ -187,6 +187,51 @@ and compare_device_names a b = ) ) +let has_bogus_mbr device = + try + with_openfile device [O_RDONLY; O_CLOEXEC] 0 (fun fd -> + let sec0size = 0x200 + and sigofs = 0x1FE + and sysidofs = 0x003 and sysidsize = 0x008 + and pte1ofs = 0x1BE + and parttypes = [0x01; (* FAT12 *) + 0x04; (* FAT16 *) + 0x06; (* FAT12, FAT16, FAT16B *) + 0x0C; (* FAT32 LBA *) + 0x0E (* FAT16B LBA *)] in + let sec0 = Bytes.create sec0size in + let sec0read = read fd sec0 0 sec0size in + let sec0at = fun offset -> Bytes.get_uint8 sec0 offset in + + (* sector read completely *) + sec0read = sec0size && + + (* boot signature present *) + sec0at (sigofs ) = 0x55 && + sec0at (sigofs + 0x1) = 0xAA && + + (* mkfs.fat signature present *) + Bytes.sub_string sec0 sysidofs sysidsize = "mkfs.fat" && + + (* partition bootable *) + sec0at (pte1ofs ) = 0x80 && + + (* partition starts at C/H/S 0/0/1 *) + sec0at (pte1ofs + 0x1) = 0x00 && + sec0at (pte1ofs + 0x2) = 0x01 && + sec0at (pte1ofs + 0x3) = 0x00 && + + (* partition type is a FAT variant that mkfs.fat is known to create *) + List.mem (sec0at (pte1ofs + 0x4)) parttypes && + + (* partition starts at LBA 0 *) + sec0at (pte1ofs + 0x8) = 0x00 && + sec0at (pte1ofs + 0x9) = 0x00 && + sec0at (pte1ofs + 0xA) = 0x00 && + sec0at (pte1ofs + 0xB) = 0x00 + ) + with _ -> false + let proc_unmangle_path path = let n = String.length path in let b = Buffer.create n in -- 2.19.1.3.g30247aa5d201

On 11/25/21 11:15, Richard W.M. Jones wrote: The book I've been learning from uses these forms interchangeably. More precisely, it gives the "fun" form as the main one, and then says, "Since named functions are so common, OCaml provides an alternative syntax for functions using a let definition". It provides the following examples, and states that they are equivalent: let sum = fun i j -> i + j;; let sum = (fun i -> (fun j -> i + j));; let sum i j = i + j;; Why is the usage of "fun" awkward here? Is the problem more that I used an explicit "offset" parameter, so sec0at is not defined as a partial function application? Thanks! Laszlo

The "is_partition_can_hold_filesystem" function calls "Parted.part_get_gpt_type" on the partition if: - the partition table type is GPT, - or the partition table type is MBR, and the partition is primary or logical. The one entry in the fake MBR partition table described in the previous patch passes the second branch of this check, therefore "Parted.part_get_gpt_type" is reached, and it invokes "sgdisk -i 1" on the disk. Surprisingly (not), while "sgdisk -i" copes fine with valid MBR partition tables, it chokes on the fake one. The output does not contain the "Partition GUID code" line, and so "sgdisk_info_extract_field" throws an exception. Prevent calling "Parted.part_get_gpt_type" on a bogus MBR partition table, similarly to the "extended entry in MBR partition table" case; the difference is that the bogus primary entry, unlike a valid extended entry, *can* hold a filesystem. Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1931821 Signed-off-by: Laszlo Ersek <lersek(a)redhat.com&gt; Acked-by: Richard W.M. Jones <rjones(a)redhat.com&gt; --- Notes: v3: - pick up Rich's ACK v2: - new patch (sigh) daemon/listfs.ml | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/daemon/listfs.ml b/daemon/listfs.ml index d8add5005ade..63ced260a14d 100644 --- a/daemon/listfs.ml +++ b/daemon/listfs.ml @@ -109,6 +109,8 @@ and is_partition_can_hold_filesystem partition = if is_gpt_or_mbr then ( if is_mbr_extended parttype device partnum then false + else if is_mbr_bogus parttype device partnum then + true else ( (* MBR partition id will be converted into corresponding GPT type. *) let gpt_type = Parted.part_get_gpt_type device partnum in @@ -130,6 +132,9 @@ and is_mbr_extended parttype device partnum = parttype = "msdos" && Parted.part_get_mbr_part_type device partnum = "extended" +and is_mbr_bogus parttype device partnum = + parttype = "msdos" && partnum = 1 && Utils.has_bogus_mbr device + (* Use vfs-type to check for a filesystem of some sort of [device]. * Appends (device, vfs_type) to the ret parameter (there may be * multiple devices found in the case of btrfs). -- 2.19.1.3.g30247aa5d201