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tracing/probes: Fix potential underflow in LEN_OR_ZERO macro

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In __set_print_fmt(), LEN_OR_ZERO is defined as (len ? len - pos : 0).
If len is non-zero but smaller than pos, len - pos evaluates to a negative
integer. When passed as a size argument to snprintf(), this negative value
is cast to a large unsigned size_t, bypassing buffer size limits.

Ensure len > pos before subtracting to avoid integer underflow.

Link: https://lore.kernel.org/all/178454234934.290363.15247317871499514139.stgit@devnote2/

Fixes: 5bf652aaf4 ("tracing/probes: Integrate duplicate set_print_fmt()")
Cc: stable@vger.kernel.org
Assisted-by: Antigravity:gemini-3.5-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
This commit is contained in:
Masami Hiramatsu (Google) 2026-07-20 19:12:29 +09:00
parent a9d6fb2840
commit 8ce20bfba4
1 changed files with 1 additions and 1 deletions
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2
kernel/trace/trace_probe.c
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@ -2013,7 +2013,7 @@ int traceprobe_update_arg(struct probe_arg *arg)
}
/* When len=0, we just calculate the needed length */
#define LEN_OR_ZERO (len ? len - pos : 0)
#define LEN_OR_ZERO (len > pos ? len - pos : 0)
static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
enum probe_print_type ptype)
{