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From: david.laight.linux@gmail.com
To: linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
	linux-trace-kernel@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	KP Singh <kpsingh@kernel.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Matt Bobrowski <mattbobrowski@google.com>,
	Song Liu <song@kernel.org>, Steven Rostedt <rostedt@goodmis.org>,
	David Laight <david.laight.linux@gmail.com>
Subject: [PATCH 35/44] bpf: use min() instead of min_t()
Date: Wed, 19 Nov 2025 22:41:31 +0000	[thread overview]
Message-ID: <20251119224140.8616-36-david.laight.linux@gmail.com> (raw)
In-Reply-To: <20251119224140.8616-1-david.laight.linux@gmail.com>

From: David Laight <david.laight.linux@gmail.com>

min_t(unsigned int, a, b) casts an 'unsigned long' to 'unsigned int'.
Use min(a, b) instead as it promotes any 'unsigned int' to 'unsigned long'
and so cannot discard significant bits.

In this case the 'unsigned long' value is small enough that the result
is ok.

Detected by an extra check added to min_t().

Signed-off-by: David Laight <david.laight.linux@gmail.com>
---
 kernel/trace/bpf_trace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 4f87c16d915a..ee3152df767c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1515,7 +1515,7 @@ BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx,
 	if (!buf || (size % br_entry_size != 0))
 		return -EINVAL;
 
-	to_copy = min_t(u32, br_stack->nr * br_entry_size, size);
+	to_copy = min(br_stack->nr * br_entry_size, size);
 	memcpy(buf, br_stack->entries, to_copy);
 
 	return to_copy;
-- 
2.39.5


  parent reply	other threads:[~2025-11-19 22:42 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-11-19 22:40 [PATCH 00/44] Change a lot of min_t() that might mask high bits david.laight.linux
2025-11-19 22:41 ` [PATCH 06/44] bpf: Verifier, remove some unusual uses of min_t() and max_t() david.laight.linux
2025-11-21 21:40   ` Alexei Starovoitov
2025-11-21 22:21     ` David Laight
2025-11-23 16:39       ` Alexei Starovoitov
2025-11-23 18:07         ` David Laight
2025-11-23 19:20           ` Alexei Starovoitov
2025-11-23 23:03             ` David Laight
2025-11-19 22:41 ` [PATCH 34/44] bpf: use min() instead of min_t() david.laight.linux
2025-11-19 22:41 ` david.laight.linux [this message]
2025-11-19 22:41 ` [PATCH 41/44] net/core: Change loop conditions so min() can be used david.laight.linux
2025-11-20  1:47 ` [PATCH 00/44] Change a lot of min_t() that might mask high bits Jakub Kicinski
2025-11-20  9:38 ` Lorenzo Stoakes
2025-11-20 14:52 ` (subset) " Jens Axboe
2025-11-24  9:49 ` Herbert Xu

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