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printk: Fix signed integer overflow when defining LOG_BUF_LEN_MAX

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[ Upstream commit 3d6f83df8ff2d5de84b50377e4f0d45e25311c7a ]

Shifting 1 << 31 on a 32-bit int causes signed integer overflow, which
leads to undefined behavior. To prevent this, cast 1 to u32 before
performing the shift, ensuring well-defined behavior.

This change explicitly avoids any potential overflow by ensuring that
the shift occurs on an unsigned 32-bit integer.

Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Acked-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240928113608.1438087-1-visitorckw@gmail.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kuan-Wei Chiu 2024-09-28 19:36:08 +08:00 • committed by Greg Kroah-Hartman
commit 54c14022fa
1 changed files with 1 additions and 1 deletions
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2
kernel/printk/printk.c
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@ -457,7 +457,7 @@ static u32 clear_idx;
/* record buffer */
#define LOG_ALIGN __alignof__(struct printk_log)
#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
#define LOG_BUF_LEN_MAX (u32)(1 << 31)
#define LOG_BUF_LEN_MAX ((u32)1 << 31)
static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
static char *log_buf = __log_buf;
static u32 log_buf_len = __LOG_BUF_LEN;