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Mon, 22 Sep 2025 10:04:27 -0700 (PDT) Received: from debian.domain.name ([223.181.114.23]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-26980310e41sm138227825ad.108.2025.09.22.10.04.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Sep 2025 10:04:27 -0700 (PDT) From: I Viswanath To: vbabka@suse.cz, akpm@linux-foundation.org, cl@gentwo.org, rientjes@google.com, roman.gushchin@linux.dev, harry.yoo@oracle.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, david.hunter.linux@gmail.com, linux-kernel-mentees@lists.linux.dev, I Viswanath , syzbot+94d20db923b9f51be0df@syzkaller.appspotmail.com Subject: [RFC PATCH] mm/slab: Add size validation in kmalloc_array_* functions Date: Mon, 22 Sep 2025 22:33:57 +0530 Message-ID: <20250922170357.148588-1-viswanathiyyappan@gmail.com> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" syzbot reported WARNING in max_vclocks_store. This occurs when the size argument fits into a u32 but is too large=20 to allocate, i.e., when it's between KMALLOC_MAX_SIZE + 1=20 and UINT_MAX (both limits included) Add validation to kmalloc_array_noprof() and related functions to=20 return early if the requested size exceeds KMALLOC_MAX_SIZE. This seems like the most reasonable place for this guard. Would it be a good idea to move the check down to=20 the lower level functions like __kmalloc_node_noprof()? Moving it up is not a good idea because max_vclocks_store shouldn't reason around KMALLOC_MAX_SIZE,=20 a mm specific macro. Should the Fixes: commit here be the one in which this file=20 was added? Reported-by: syzbot+94d20db923b9f51be0df@syzkaller.appspotmail.com Tested-by: syzbot+94d20db923b9f51be0df@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D94d20db923b9f51be0df Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: I Viswanath --- include/linux/slab.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/include/linux/slab.h b/include/linux/slab.h index d5a8ab98035c..6db15c5b2ce7 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -943,7 +943,7 @@ static inline __alloc_size(1, 2) void *kmalloc_array_no= prof(size_t n, size_t siz { size_t bytes; =20 - if (unlikely(check_mul_overflow(n, size, &bytes))) + if (unlikely(check_mul_overflow(n, size, &bytes) || (bytes > KMALLOC_MAX_= SIZE))) return NULL; return kmalloc_noprof(bytes, flags); } @@ -973,7 +973,7 @@ static inline __realloc_size(2, 3) void * __must_check = krealloc_array_noprof(voi { size_t bytes; =20 - if (unlikely(check_mul_overflow(new_n, new_size, &bytes))) + if (unlikely(check_mul_overflow(new_n, new_size, &bytes) || (bytes > KMAL= LOC_MAX_SIZE))) return NULL; =20 return krealloc_noprof(p, bytes, flags); @@ -1013,7 +1013,7 @@ static inline __alloc_size(1, 2) void *kmalloc_array_= node_noprof(size_t n, size_ { size_t bytes; =20 - if (unlikely(check_mul_overflow(n, size, &bytes))) + if (unlikely(check_mul_overflow(n, size, &bytes) || (bytes > KMALLOC_MAX_= SIZE))) return NULL; if (__builtin_constant_p(n) && __builtin_constant_p(size)) return kmalloc_node_noprof(bytes, flags, node); @@ -1059,7 +1059,7 @@ kvmalloc_array_node_noprof(size_t n, size_t size, gfp= _t flags, int node) { size_t bytes; =20 - if (unlikely(check_mul_overflow(n, size, &bytes))) + if (unlikely(check_mul_overflow(n, size, &bytes) || (bytes > KMALLOC_MAX_= SIZE))) return NULL; =20 return kvmalloc_node_noprof(bytes, flags, node); --=20 2.47.3