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 <[email protected]> --- 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); -- 2.43.0
