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Unrated severityNVD Advisory· Published May 27, 2026· Updated May 27, 2026

CVE-2026-46022

CVE-2026-46022

Description

In the Linux kernel, the following vulnerability has been resolved:

misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()

ibmasm_handle_mouse_interrupt() performs an out-of-bounds MMIO read when the queue reader or writer index from hardware exceeds REMOTE_QUEUE_SIZE (60).

A compromised service processor can trigger this by writing an out-of-range value to the reader or writer MMIO register before asserting an interrupt. Since writer is re-read from hardware on every loop iteration, it can also be set to an out-of-range value after the loop has already started.

The root cause is that get_queue_reader() and get_queue_writer() return raw readl() values that are passed directly into get_queue_entry(), which computes:

queue_begin + reader * sizeof(struct remote_input)

with no bounds check. This unchecked MMIO address is then passed to memcpy_fromio(), reading 8 bytes from unintended device registers. For sufficiently large values the address falls outside the PCI BAR mapping entirely, triggering a machine check exception.

Fix by checking both indices against REMOTE_QUEUE_SIZE at the top of the loop body, before any call to get_queue_entry(). On an out-of-range value, reset the reader register to 0 via set_queue_reader() before breaking, so that normal queue operation can resume if the corrupted hardware state is transient.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

In Linux kernel's ibmasm driver, unvalidated queue indices cause OOB MMIO read, enabling a compromised service processor to cause a machine check exception.

Vulnerability

In the Linux kernel's ibmasm driver, the function ibmasm_handle_mouse_interrupt() performs an out-of-bounds MMIO read when the queue reader or writer index obtained from hardware exceeds REMOTE_QUEUE_SIZE (60). The indices are read via get_queue_reader() and get_queue_writer(), which return raw readl() values without bounds checking. These values are passed to get_queue_entry(), which computes queue_begin + reader * sizeof(struct remote_input) and passes the resulting address to memcpy_fromio(), reading 8 bytes from unintended device registers or, for sufficiently large values, outside the PCI BAR mapping. Affected versions are those prior to the fix commit [1].

Exploitation

An attacker must have control over the service processor that communicates with the host via MMIO registers. The attacker writes an out-of-range value (≥60) to the reader or writer MMIO register and then asserts an interrupt. The driver's interrupt handler reads the out-of-range index and computes an invalid MMIO address. Since the writer index is re-read from hardware on every loop iteration, the attacker can also change it to an out-of-range value after the loop has started, prolonging the OOB access.

Impact

The out-of-bounds MMIO read can read from unintended device registers, and for large index values the address falls outside the PCI BAR mapping, triggering a machine check exception (MCE). This results in a denial of service (system crash). No privilege escalation or information disclosure is described.

Mitigation

The vulnerability is fixed in Linux kernel commit 07c4f18b3031 [1]. The fix adds bounds checks for both indices against REMOTE_QUEUE_SIZE at the top of the loop body and resets the reader register to 0 on an out-of-range value before breaking. Users should apply the patch from the stable kernel tree. No workaround is available.

References
  1. Making sure you're not a bot!

AI Insight generated on May 27, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

1

Patches

10
07c4f18b3031

misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitTyllis XuFixed in 6.12.86via kernel-cna
commit
1 file changed · +5 −1
  • drivers/misc/ibmasm/remote.c+5 −1 modified
    diff --git a/drivers/misc/ibmasm/remote.c b/drivers/misc/ibmasm/remote.c
index ec816d3b38cbd4..521531738c9af3 100644
--- a/drivers/misc/ibmasm/remote.c
+++ b/drivers/misc/ibmasm/remote.c
@@ -177,6 +177,11 @@ void ibmasm_handle_mouse_interrupt(struct service_processor *sp)
 	writer = get_queue_writer(sp);
 
 	while (reader != writer) {
+		if (reader >= REMOTE_QUEUE_SIZE || writer >= REMOTE_QUEUE_SIZE) {
+			set_queue_reader(sp, 0);
+			break;
+		}
+
 		memcpy_fromio(&input, get_queue_entry(sp, reader),
 				sizeof(struct remote_input));
 
-- 
cgit 1.3-korg
fc7e9a74e322

misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitTyllis XuFixed in 6.6.140via kernel-cna
commit
1 file changed · +5 −1
  • drivers/misc/ibmasm/remote.c+5 −1 modified
    diff --git a/drivers/misc/ibmasm/remote.c b/drivers/misc/ibmasm/remote.c
index ec816d3b38cbd4..521531738c9af3 100644
--- a/drivers/misc/ibmasm/remote.c
+++ b/drivers/misc/ibmasm/remote.c
@@ -177,6 +177,11 @@ void ibmasm_handle_mouse_interrupt(struct service_processor *sp)
 	writer = get_queue_writer(sp);
 
 	while (reader != writer) {
+		if (reader >= REMOTE_QUEUE_SIZE || writer >= REMOTE_QUEUE_SIZE) {
+			set_queue_reader(sp, 0);
+			break;
+		}
+
 		memcpy_fromio(&input, get_queue_entry(sp, reader),
 				sizeof(struct remote_input));
 
-- 
cgit 1.3-korg
1ca75f6b74ec

misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitTyllis XuFixed in 7.0.4via kernel-cna
commit
1 file changed · +5 −1
  • drivers/misc/ibmasm/remote.c+5 −1 modified
    diff --git a/drivers/misc/ibmasm/remote.c b/drivers/misc/ibmasm/remote.c
index ec816d3b38cbd4..521531738c9af3 100644
--- a/drivers/misc/ibmasm/remote.c
+++ b/drivers/misc/ibmasm/remote.c
@@ -177,6 +177,11 @@ void ibmasm_handle_mouse_interrupt(struct service_processor *sp)
 	writer = get_queue_writer(sp);
 
 	while (reader != writer) {
+		if (reader >= REMOTE_QUEUE_SIZE || writer >= REMOTE_QUEUE_SIZE) {
+			set_queue_reader(sp, 0);
+			break;
+		}
+
 		memcpy_fromio(&input, get_queue_entry(sp, reader),
 				sizeof(struct remote_input));
 
-- 
cgit 1.3-korg
4b6e6ead5567

misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitTyllis XuFixed in 7.1-rc1via kernel-cna
commit
1 file changed · +5 −1
  • drivers/misc/ibmasm/remote.c+5 −1 modified
    diff --git a/drivers/misc/ibmasm/remote.c b/drivers/misc/ibmasm/remote.c
index ec816d3b38cbd4..521531738c9af3 100644
--- a/drivers/misc/ibmasm/remote.c
+++ b/drivers/misc/ibmasm/remote.c
@@ -177,6 +177,11 @@ void ibmasm_handle_mouse_interrupt(struct service_processor *sp)
 	writer = get_queue_writer(sp);
 
 	while (reader != writer) {
+		if (reader >= REMOTE_QUEUE_SIZE || writer >= REMOTE_QUEUE_SIZE) {
+			set_queue_reader(sp, 0);
+			break;
+		}
+
 		memcpy_fromio(&input, get_queue_entry(sp, reader),
 				sizeof(struct remote_input));
 
-- 
cgit 1.3-korg
22a16d3eafee

misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitTyllis XuFixed in 6.18.27via kernel-cna
commit
1 file changed · +5 −1
  • drivers/misc/ibmasm/remote.c+5 −1 modified
    diff --git a/drivers/misc/ibmasm/remote.c b/drivers/misc/ibmasm/remote.c
index ec816d3b38cbd4..521531738c9af3 100644
--- a/drivers/misc/ibmasm/remote.c
+++ b/drivers/misc/ibmasm/remote.c
@@ -177,6 +177,11 @@ void ibmasm_handle_mouse_interrupt(struct service_processor *sp)
 	writer = get_queue_writer(sp);
 
 	while (reader != writer) {
+		if (reader >= REMOTE_QUEUE_SIZE || writer >= REMOTE_QUEUE_SIZE) {
+			set_queue_reader(sp, 0);
+			break;
+		}
+
 		memcpy_fromio(&input, get_queue_entry(sp, reader),
 				sizeof(struct remote_input));
 
-- 
cgit 1.3-korg
1ca75f6b74ec

misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitTyllis Xuvia nvd-ref
commit
1 file changed · +5 −1
  • drivers/misc/ibmasm/remote.c+5 −1 modified
    diff --git a/drivers/misc/ibmasm/remote.c b/drivers/misc/ibmasm/remote.c
index ec816d3b38cbd4..521531738c9af3 100644
--- a/drivers/misc/ibmasm/remote.c
+++ b/drivers/misc/ibmasm/remote.c
@@ -177,6 +177,11 @@ void ibmasm_handle_mouse_interrupt(struct service_processor *sp)
 	writer = get_queue_writer(sp);
 
 	while (reader != writer) {
+		if (reader >= REMOTE_QUEUE_SIZE || writer >= REMOTE_QUEUE_SIZE) {
+			set_queue_reader(sp, 0);
+			break;
+		}
+
 		memcpy_fromio(&input, get_queue_entry(sp, reader),
 				sizeof(struct remote_input));
 
-- 
cgit 1.3-korg
22a16d3eafee

misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitTyllis Xuvia nvd-ref
commit
1 file changed · +5 −1
  • drivers/misc/ibmasm/remote.c+5 −1 modified
    diff --git a/drivers/misc/ibmasm/remote.c b/drivers/misc/ibmasm/remote.c
index ec816d3b38cbd4..521531738c9af3 100644
--- a/drivers/misc/ibmasm/remote.c
+++ b/drivers/misc/ibmasm/remote.c
@@ -177,6 +177,11 @@ void ibmasm_handle_mouse_interrupt(struct service_processor *sp)
 	writer = get_queue_writer(sp);
 
 	while (reader != writer) {
+		if (reader >= REMOTE_QUEUE_SIZE || writer >= REMOTE_QUEUE_SIZE) {
+			set_queue_reader(sp, 0);
+			break;
+		}
+
 		memcpy_fromio(&input, get_queue_entry(sp, reader),
 				sizeof(struct remote_input));
 
-- 
cgit 1.3-korg
4b6e6ead5567

misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitTyllis Xuvia nvd-ref
commit
1 file changed · +5 −1
  • drivers/misc/ibmasm/remote.c+5 −1 modified
    diff --git a/drivers/misc/ibmasm/remote.c b/drivers/misc/ibmasm/remote.c
index ec816d3b38cbd4..521531738c9af3 100644
--- a/drivers/misc/ibmasm/remote.c
+++ b/drivers/misc/ibmasm/remote.c
@@ -177,6 +177,11 @@ void ibmasm_handle_mouse_interrupt(struct service_processor *sp)
 	writer = get_queue_writer(sp);
 
 	while (reader != writer) {
+		if (reader >= REMOTE_QUEUE_SIZE || writer >= REMOTE_QUEUE_SIZE) {
+			set_queue_reader(sp, 0);
+			break;
+		}
+
 		memcpy_fromio(&input, get_queue_entry(sp, reader),
 				sizeof(struct remote_input));
 
-- 
cgit 1.3-korg
fc7e9a74e322

misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitTyllis Xuvia nvd-ref
commit
1 file changed · +5 −1
  • drivers/misc/ibmasm/remote.c+5 −1 modified
    diff --git a/drivers/misc/ibmasm/remote.c b/drivers/misc/ibmasm/remote.c
index ec816d3b38cbd4..521531738c9af3 100644
--- a/drivers/misc/ibmasm/remote.c
+++ b/drivers/misc/ibmasm/remote.c
@@ -177,6 +177,11 @@ void ibmasm_handle_mouse_interrupt(struct service_processor *sp)
 	writer = get_queue_writer(sp);
 
 	while (reader != writer) {
+		if (reader >= REMOTE_QUEUE_SIZE || writer >= REMOTE_QUEUE_SIZE) {
+			set_queue_reader(sp, 0);
+			break;
+		}
+
 		memcpy_fromio(&input, get_queue_entry(sp, reader),
 				sizeof(struct remote_input));
 
-- 
cgit 1.3-korg
07c4f18b3031

misc: ibmasm: fix OOB MMIO read in ibmasm_handle_mouse_interrupt()

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.gitTyllis Xuvia nvd-ref
commit
1 file changed · +5 −1
  • drivers/misc/ibmasm/remote.c+5 −1 modified
    diff --git a/drivers/misc/ibmasm/remote.c b/drivers/misc/ibmasm/remote.c
index ec816d3b38cbd4..521531738c9af3 100644
--- a/drivers/misc/ibmasm/remote.c
+++ b/drivers/misc/ibmasm/remote.c
@@ -177,6 +177,11 @@ void ibmasm_handle_mouse_interrupt(struct service_processor *sp)
 	writer = get_queue_writer(sp);
 
 	while (reader != writer) {
+		if (reader >= REMOTE_QUEUE_SIZE || writer >= REMOTE_QUEUE_SIZE) {
+			set_queue_reader(sp, 0);
+			break;
+		}
+
 		memcpy_fromio(&input, get_queue_entry(sp, reader),
 				sizeof(struct remote_input));
 
-- 
cgit 1.3-korg

Vulnerability mechanics

Root cause

"Missing bounds check on queue reader/writer indices from hardware allows out-of-bounds MMIO read in ibmasm_handle_mouse_interrupt()."

Attack vector

A compromised service processor writes an out-of-range value to the reader or writer MMIO register before asserting an interrupt. Since the writer is re-read from hardware on every loop iteration, it can also be set to an out-of-range value after the loop has already started. The functions get_queue_reader() and get_queue_writer() return raw readl() values that are passed directly into get_queue_entry(), which computes queue_begin + reader * sizeof(struct remote_input) with no bounds check. This unchecked MMIO address is then passed to memcpy_fromio(), reading 8 bytes from unintended device registers; for sufficiently large values the address falls outside the PCI BAR mapping entirely, triggering a machine check exception.

Affected code

The vulnerable function is ibmasm_handle_mouse_interrupt() in drivers/misc/ibmasm/remote.c. The functions get_queue_reader() and get_queue_writer() return raw readl() values that are passed without bounds checking into get_queue_entry(), which computes queue_begin + reader * sizeof(struct remote_input).

What the fix does

The patch adds a bounds check at the top of the while loop body in ibmasm_handle_mouse_interrupt() in drivers/misc/ibmasm/remote.c [patch_id=2660371]. If either reader or writer is >= REMOTE_QUEUE_SIZE (60), the reader register is reset to 0 via set_queue_reader() and the loop breaks. This prevents any call to get_queue_entry() with an out-of-range index, closing the OOB MMIO read. Resetting the reader to 0 allows normal queue operation to resume if the corrupted hardware state is transient.

Preconditions

  • authAttacker must compromise the service processor (the hardware device that communicates with the host via MMIO registers)
  • inputThe compromised service processor must be able to write arbitrary values to the queue reader or writer MMIO registers
  • inputThe service processor must assert an interrupt to trigger ibmasm_handle_mouse_interrupt()

Generated on May 27, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

5

News mentions

0

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