[xen staging] x86/pmstat: Check size of PMSTAT_get_pxstat buffers

[patchbot@xxxxxxx]

commit aa70996a6896dfc9de60f60540098b7d3ac3fb4f
Author:     Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
AuthorDate: Wed Jun 11 11:05:42 2025 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jun 11 11:05:42 2025 +0200

    x86/pmstat: Check size of PMSTAT_get_pxstat buffers
    
    Check that the total number of states passed in and hence the size of
    buffers is sufficient to avoid writing more than the caller has
    allocated.
    
    The interface is not explicit about whether getpx.total is expected to
    be set by the caller in this case but since it is always set in
    libxenctrl it seems reasonable to check it and make it explicit.
    
    Fixes: c06a7db0c547 ("X86 and IA64: Update cpufreq statistic logic for 
supporting both x86 and ia64")
    Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/drivers/acpi/pmstat.c   |  7 +++++--
 xen/include/public/sysctl.h | 15 +++++++++++++--
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/xen/drivers/acpi/pmstat.c b/xen/drivers/acpi/pmstat.c
index c51b9ca358..0d570e28bf 100644
--- a/xen/drivers/acpi/pmstat.c
+++ b/xen/drivers/acpi/pmstat.c
@@ -103,8 +103,11 @@ int do_get_pm_info(struct xen_sysctl_get_pmstat *op)
 
         cpufreq_residency_update(op->cpuid, pxpt->u.cur);
 
-        ct = pmpt->perf.state_count;
-        if ( copy_to_guest(op->u.getpx.trans_pt, pxpt->u.trans_pt, ct*ct) )
+        ct = min(pmpt->perf.state_count, op->u.getpx.total + 0U);
+
+        /* Avoid partial copying of 2-D array */
+        if ( ct == op->u.getpx.total &&
+             copy_to_guest(op->u.getpx.trans_pt, pxpt->u.trans_pt, ct * ct) )
         {
             spin_unlock(cpufreq_statistic_lock);
             ret = -EFAULT;
diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h
index 9eca72865b..c804abb8b9 100644
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -215,11 +215,22 @@ typedef struct pm_px_val pm_px_val_t;
 DEFINE_XEN_GUEST_HANDLE(pm_px_val_t);
 
 struct pm_px_stat {
-    uint8_t total;        /* total Px states */
+    /*
+     * IN: Number of elements in pt, number of rows/columns in trans_pt
+     *     (PMSTAT_get_pxstat)
+     * OUT: total Px states (PMSTAT_get_max_px, PMSTAT_get_pxstat)
+     */
+    uint8_t total;
     uint8_t usable;       /* usable Px states */
     uint8_t last;         /* last Px state */
     uint8_t cur;          /* current Px state */
-    XEN_GUEST_HANDLE_64(uint64) trans_pt;   /* Px transition table */
+    /*
+     * OUT: Px transition table. This should have total * total elements.
+     *      As it is a 2-D array, this will not be copied if input total is
+     *      less than output total. (PMSTAT_get_pxstat)
+     */
+    XEN_GUEST_HANDLE_64(uint64) trans_pt;
+    /* OUT: This should have total elements (PMSTAT_get_pxstat) */
     XEN_GUEST_HANDLE_64(pm_px_val_t) pt;
 };
 
--
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