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X-CSE-ConnectionGUID: 5NcFcmAwSh+bG6qW5lb2GQ== X-CSE-MsgGUID: pd8DuHJFS+aleHQX5/LW2Q== X-IronPort-AV: E=McAfee;i="6800,10657,11531"; a="62667497" X-IronPort-AV: E=Sophos;i="6.17,312,1747724400"; d="scan'208";a="62667497" Received: from fmviesa001.fm.intel.com ([10.60.135.141]) by orvoesa106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Aug 2025 10:21:52 -0700 X-CSE-ConnectionGUID: Jfuuo0EHR4Wm5UB3Y/DJpA== X-CSE-MsgGUID: DmgXPHlHSZ6zLrCKKM2ztA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,225,1751266800"; d="scan'208";a="201524084" Received: from baandr0id001.iind.intel.com ([10.66.253.151]) by fmviesa001.fm.intel.com with ESMTP; 30 Aug 2025 10:21:50 -0700 From: Kaushlendra Kumar To: akpm@linux-foundation.org Cc: linux-mm@kvack.org, Kaushlendra Kumar Subject: [PATCH v2] tools/mm/slabinfo: fix access to null terminator in string boundary Date: Sat, 30 Aug 2025 22:50:22 +0530 Message-Id: <20250830172022.1927448-1-kaushlendra.kumar@intel.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: D6C50160014 X-Stat-Signature: 359hqbc137h5ggqk7857pog4j16j8ix4 X-HE-Tag: 1756574512-565388 X-HE-Meta: U2FsdGVkX18s+fW2h77Q02223x2U8+opJzjstrOgGzhRqEFewEs7CASQm/qeL9ryXOWjc5+cuqiCzHecHzPw0/3rcOUMYzOzyMlBa3NXHW+5Mlyf1eWdvjcjkDRfEbGMrBWitvoLhU49YDsirEXNR0YX0eUc1HnuyepnzmaHJURuI+dgz0vtoE5cIk4rJun8VTYkOCer2W47zvRHioZQ/e5A35wTUX/ZeSXZ9H8VCl9qb2vMuT+7vpXzVFOM2jPX0oACQoZODA3K8WwprL9Fk5pPVTZWMsejdC4XiAxeG7uQAFY91ZuC92iNHPOzeEn1NujeyiafRWSCoeIl5Cp1D41OKixKazYLg0abeRstt2wQNthTp9hf5sVeKwFgRU5kvayNS+XYJ9EmiLZR2X3r25lWV6cTxcOTQbyFNvKKYiN5CH89AGsgTaW0qTlKwxbrtkwPNuHJngNM/L8Ifp4pv8y4DtWtHJ13Ka+WzNbiKyXtJINti1AvQpXkxEO+2IW/iv5uIuFqVhpdAIUHArGThWeBZUzwf15KfkXUDR4Lcle930qJ1jGY3sAj3To6WfaIT9fd3ACiRbxumMHW05ILTeTO/hI3kqAoZhJAEv2xZww50eO/ZsOQaK/77DRQzK/0m23QSnUKrJrLuRUAx6fiTvAWinMfitTGGvmG+ENtfYUvS3LhK3mytl7NWIouDuJkeNKTdtbsDw4/rH0Nz5INVjJU7r+dsWj+BVaBnD0FrpR/9/KHcbMitwQknjDbK3eYfAzLw2GP10bVv4sqwqqD3MGAB4Pd5V/D67YrGql8ijrCTm4AjQUA93SJwog8K/mT9smAniEeYNjmKmsNU+s7k7WfRM91Ln1Z3V2YZlOruvUpj2L92CI5tKIvHAj7V3UqEEazpOB3MvRGOzIQmfcHpq5COSNs90VnTzUuXjXGGajNCf1P9FzL6WR8YInW+qmapL1++psR3cGRazpFFYy 9cohOLNO C1ZT6c154ls9g5Hj1ZNGs9pQwEG/WP92uIPs2/sfvGWW3AUR3tkLn7+4OH5u18UHiet7UDbZeiDHNS6pgZaQ3EY7NYdqMPt1JaycqfitBq6pCMRA59opoQEIVGJ4JYzlpWmMZopCvyqHCsRWlOKn0BULrrcKz/elgyoiMEDoIJq9MCGQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The current code incorrectly accesses buffer[strlen(buffer)], which points to the null terminator ('\0') at the end of the string. This is technically out-of-bounds access since valid string content ends at index strlen(buffer)-1. Fix by: 1. Declaring strlen() result variable at function scope 2. Adding bounds check (len > 0) to handle empty strings 3. Using buffer[len-1] to correctly access the last character before the null terminator v2: Move variable declaration to function scope to avoid mixing declarations with statements (feedback from reviewer) Signed-off-by: Kaushlendra Kumar --- tools/mm/slabinfo.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/tools/mm/slabinfo.c b/tools/mm/slabinfo.c index 1433eff99feb..d2e5b4e232b1 100644 --- a/tools/mm/slabinfo.c +++ b/tools/mm/slabinfo.c @@ -155,6 +155,8 @@ static void usage(void) static unsigned long read_obj(const char *name) { + size_t len; + FILE *f = fopen(name, "r"); if (!f) { @@ -165,8 +167,10 @@ static unsigned long read_obj(const char *name) if (!fgets(buffer, sizeof(buffer), f)) buffer[0] = 0; fclose(f); - if (buffer[strlen(buffer)] == '\n') - buffer[strlen(buffer)] = 0; + len = strlen(buffer); + + if (len > 0 && buffer[len - 1] == '\n') + buffer[len - 1] = 0; } return strlen(buffer); } -- 2.34.1