AI Score
Confidence
High
EPSS
Percentile
13.0%
SSVC
Exploitation
none
Automatable
no
Technical Impact
partial
In the Linux kernel, the following vulnerability has been resolved:
VMCI: Fix memcpy() run-time warning in dg_dispatch_as_host()
Syzkaller hit ‘WARNING in dg_dispatch_as_host’ bug.
memcpy: detected field-spanning write (size 56) of single field “&dg_info->msg”
at drivers/misc/vmw_vmci/vmci_datagram.c:237 (size 24)
WARNING: CPU: 0 PID: 1555 at drivers/misc/vmw_vmci/vmci_datagram.c:237
dg_dispatch_as_host+0x88e/0xa60 drivers/misc/vmw_vmci/vmci_datagram.c:237
Some code commentry, based on my understanding:
544 #define VMCI_DG_SIZE(_dg) (VMCI_DG_HEADERSIZE + (size_t)(_dg)->payload_size)
/// This is 24 + payload_size
memcpy(&dg_info->msg, dg, dg_size);
Destination = dg_info->msg —> this is a 24 byte
structure(struct vmci_datagram)
Source = dg –> this is a 24 byte structure (struct vmci_datagram)
Size = dg_size = 24 + payload_size
{payload_size = 56-24 =32} – Syzkaller managed to set payload_size to 32.
35 struct delayed_datagram_info {
36 struct datagram_entry entry;
37 struct work_struct work;
38 bool in_dg_host_queue;
39 / msg and msg_payload must be together. */
40 struct vmci_datagram msg;
41 u8 msg_payload[];
42 };
So those extra bytes of payload are copied into msg_payload[], a run time
warning is seen while fuzzing with Syzkaller.
One possible way to fix the warning is to split the memcpy() into
two parts – one – direct assignment of msg and second taking care of payload.
Gustavo quoted:
“Under FORTIFY_SOURCE we should not copy data across multiple members
in a structure.”
[
{
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"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "1da177e4c3f4",
"lessThan": "e87bb99d2df6",
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{
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{
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{
"status": "affected",
"version": "1da177e4c3f4",
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],
"programFiles": [
"drivers/misc/vmw_vmci/vmci_datagram.c"
],
"defaultStatus": "unaffected"
},
{
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"vendor": "Linux",
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"versions": [
{
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"version": "4.19.312",
"versionType": "custom",
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{
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},
{
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"version": "5.10.215",
"versionType": "custom",
"lessThanOrEqual": "5.10.*"
},
{
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"version": "5.15.155",
"versionType": "custom",
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},
{
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"version": "6.1.86",
"versionType": "custom",
"lessThanOrEqual": "6.1.*"
},
{
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"version": "6.6.27",
"versionType": "custom",
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},
{
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"version": "6.8.6",
"versionType": "custom",
"lessThanOrEqual": "6.8.*"
},
{
"status": "unaffected",
"version": "6.9",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"drivers/misc/vmw_vmci/vmci_datagram.c"
],
"defaultStatus": "affected"
}
]
git.kernel.org/stable/c/130b0cd064874e0d0f58e18fb00e6f3993e90c74
git.kernel.org/stable/c/19b070fefd0d024af3daa7329cbc0d00de5302ec
git.kernel.org/stable/c/491a1eb07c2bd8841d63cb5263455e185be5866f
git.kernel.org/stable/c/ad78c5047dc4076d0b3c4fad4f42ffe9c86e8100
git.kernel.org/stable/c/dae70a57565686f16089737adb8ac64471570f73
git.kernel.org/stable/c/e87bb99d2df6512d8ee37a5d63d2ca9a39a8c051
git.kernel.org/stable/c/f15eca95138b3d4ec17b63c3c1937b0aa0d3624b
git.kernel.org/stable/c/feacd430b42bbfa9ab3ed9e4f38b86c43e348c75
lists.debian.org/debian-lts-announce/2024/06/msg00017.html
lists.debian.org/debian-lts-announce/2024/06/msg00020.html