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Message-ID: <20201001145608.GA10204@embeddedor> Date: Thu, 1 Oct 2020 09:56:08 -0500 From: "Gustavo A. R. Silva" <gustavoars@...nel.org> To: Steve Wahl <steve.wahl@....com>, Dimitri Sivanich <dimitri.sivanich@....com>, Russ Anderson <russ.anderson@....com>, Darren Hart <dvhart@...radead.org>, Andy Shevchenko <andy@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com> Cc: x86@...nel.org, platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org, "Gustavo A. R. Silva" <gustavoars@...nel.org>, Kees Cook <keescook@...omium.org>, linux-hardening@...r.kernel.org Subject: [PATCH v2][next] x86/uv/time: Replace one-element array and save heap space There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. struct uv_rtc_timer_head contains a one-element array cpu[1]. Switch it to a flexible array and use the struct_size() helper to calculate the allocation size. Also, save some heap space in the process[3]. [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays [3] https://lore.kernel.org/lkml/20200518190114.GA7757@embeddedor/ Reviewed-by: Kees Cook <keescook@...omium.org> Build-tested-by: kernel test robot <lkp@...el.com> Link: https://lore.kernel.org/lkml/5f75bc0a.rQcNS6620b2eA74S%25lkp@intel.com/ Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org> --- Changes in v2: - Modify changelog text (Thomas). - Add Reviewed-by and Build-tested-by tags. - Add a public link to the build-test results. arch/x86/platform/uv/uv_time.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/arch/x86/platform/uv/uv_time.c b/arch/x86/platform/uv/uv_time.c index f82a1337a608..6c348c2d0def 100644 --- a/arch/x86/platform/uv/uv_time.c +++ b/arch/x86/platform/uv/uv_time.c @@ -52,7 +52,7 @@ struct uv_rtc_timer_head { struct { int lcpu; /* systemwide logical cpu number */ u64 expires; /* next timer expiration for this cpu */ - } cpu[1]; + } cpu[]; }; /* @@ -148,9 +148,8 @@ static __init int uv_rtc_allocate_timers(void) struct uv_rtc_timer_head *head = blade_info[bid]; if (!head) { - head = kmalloc_node(sizeof(struct uv_rtc_timer_head) + - (uv_blade_nr_possible_cpus(bid) * - 2 * sizeof(u64)), + head = kmalloc_node(struct_size(head, cpu, + uv_blade_nr_possible_cpus(bid)), GFP_KERNEL, nid); if (!head) { uv_rtc_deallocate_timers(); -- 2.27.0
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