[PATCH v1 3/4] powerpc/pseries: energy: bound H_BEST_ENERGY cnt and sysfs output
From: Xixin Liu <hidden>
Date: 2026-08-07 03:31:43
Also in:
lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
The H_BEST_ENERGY sysfs path takes cnt from the hypercall return buffer and walks buf_page[2*i+1] without checking that cnt fits in the single page allocated for the hcall, and sprintf()s into the PAGE_SIZE sysfs buffer without remaining-space checks. Clamp cnt to the number of u32 pairs that fit in the page, and stop formatting before overflowing the sysfs page. Signed-off-by: Xixin Liu <redacted> --- 1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/pseries_energy.c b/arch/powerpc/platforms/pseries/pseries_energy.c
index fdaf85ecd39b..8344f00656e5 100644
--- a/arch/powerpc/platforms/pseries/pseries_energy.c
+++ b/arch/powerpc/platforms/pseries/pseries_energy.c@@ -209,16 +209,28 @@ return -EINVAL; } + /* + * Each entry occupies two u32s in buf_page. Never walk past the + * page, and never sprintf past the PAGE_SIZE sysfs buffer. + */ cnt = retbuf[0]; + if (cnt > (PAGE_SIZE / sizeof(u32)) / 2) + cnt = (PAGE_SIZE / sizeof(u32)) / 2; + for (i = 0; i < cnt; i++) { cpu = drc_index_to_cpu(buf_page[2*i+1]); if ((cpu_online(cpu) && !activate) || - (!cpu_online(cpu) && activate)) + (!cpu_online(cpu) && activate)) { + if (s - page >= PAGE_SIZE - 16) + break; s += sprintf(s, "%d,", cpu); + } } if (s > page) { /* Something to show */ s--; /* Suppress last comma */ - s += sprintf(s, "\n"); + /* sprintf needs room for '\n' and trailing NUL. */ + if (s - page < PAGE_SIZE - 1) + s += sprintf(s, "\n"); } free_page((unsigned long) buf_page);
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2.43.0