This is a note to let you know that I've just added the patch titled
dm ioctl: fix misbehavior if list_versions races with module loading
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dm-ioctl-fix-misbehavior-if-list_versions-races-with-module-loading.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4fe1ec995483737f3d2a14c3fe1d8fe634972979 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Date: Tue, 1 Nov 2022 16:53:35 -0400
Subject: dm ioctl: fix misbehavior if list_versions races with module loading
From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
commit 4fe1ec995483737f3d2a14c3fe1d8fe634972979 upstream.
__list_versions will first estimate the required space using the
"dm_target_iterate(list_version_get_needed, &needed)" call and then will
fill the space using the "dm_target_iterate(list_version_get_info,
&iter_info)" call. Each of these calls locks the targets using the
"down_read(&_lock)" and "up_read(&_lock)" calls, however between the first
and second "dm_target_iterate" there is no lock held and the target
modules can be loaded at this point, so the second "dm_target_iterate"
call may need more space than what was the first "dm_target_iterate"
returned.
The code tries to handle this overflow (see the beginning of
list_version_get_info), however this handling is incorrect.
The code sets "param->data_size = param->data_start + needed" and
"iter_info.end = (char *)vers+len" - "needed" is the size returned by the
first dm_target_iterate call; "len" is the size of the buffer allocated by
userspace.
"len" may be greater than "needed"; in this case, the code will write up
to "len" bytes into the buffer, however param->data_size is set to
"needed", so it may write data past the param->data_size value. The ioctl
interface copies only up to param->data_size into userspace, thus part of
the result will be truncated.
Fix this bug by setting "iter_info.end = (char *)vers + needed;" - this
guarantees that the second "dm_target_iterate" call will write only up to
the "needed" buffer and it will exit with "DM_BUFFER_FULL_FLAG" if it
overflows the "needed" space - in this case, userspace will allocate a
larger buffer and retry.
Note that there is also a bug in list_version_get_needed - we need to add
"strlen(tt->name) + 1" to the needed size, not "strlen(tt->name)".
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-ioctl.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -655,7 +655,7 @@ static void list_version_get_needed(stru
size_t *needed = needed_param;
*needed += sizeof(struct dm_target_versions);
- *needed += strlen(tt->name);
+ *needed += strlen(tt->name) + 1;
*needed += ALIGN_MASK;
}
@@ -720,7 +720,7 @@ static int __list_versions(struct dm_ioc
iter_info.old_vers = NULL;
iter_info.vers = vers;
iter_info.flags = 0;
- iter_info.end = (char *)vers+len;
+ iter_info.end = (char *)vers + needed;
/*
* Now loop through filling out the names & versions.
Patches currently in stable-queue which might be from mpatocka@xxxxxxxxxx are
queue-5.15/dm-ioctl-fix-misbehavior-if-list_versions-races-with-module-loading.patch
