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Mon, 17 Feb 2025 06:08:38 -0800 (PST) From: Ryan Roberts To: Catalin Marinas , Will Deacon , Pasha Tatashin , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , David Hildenbrand , "Matthew Wilcox (Oracle)" , Mark Rutland , Anshuman Khandual , Alexandre Ghiti , Kevin Brodsky Cc: Ryan Roberts , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 08/14] mm/vmalloc: Warn on improper use of vunmap_range() Date: Mon, 17 Feb 2025 14:08:00 +0000 Message-ID: <20250217140809.1702789-9-ryan.roberts@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250217140809.1702789-1-ryan.roberts@arm.com> References: <20250217140809.1702789-1-ryan.roberts@arm.com> MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Queue-Id: 53461180010 X-Rspamd-Server: rspam07 X-Stat-Signature: t5gpi5mogxzg6p356j6ahrjucykccbb8 X-HE-Tag: 1739801321-588021 X-HE-Meta: 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 brUptJLe iKkH0D7pqRUj8AhnVWTju7RXUYtWRbLBHaj6hnb/Oy+slvlRXk+7c8DNcd+UTqm4kDOa9OAv5pcKXPQkQa/ZdDTFRxNS3aemN5jCRlpGJXASqnBJ7Ns0eDG/I7J0GXHlOzBOprD5YzVMggPXv6Cz92N0Ev1WIJQ0Mgguduk3MtfbeZQx0CbLmV5U2q8MeG9cZYea2jkoOCsmIt5o= 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: A call to vmalloc_huge() may cause memory blocks to be mapped at pmd or pud level. But it is possible to subsequently call vunmap_range() on a sub-range of the mapped memory, which partially overlaps a pmd or pud. In this case, vmalloc unmaps the entire pmd or pud so that the no-overlapping portion is also unmapped. Clearly that would have a bad outcome, but it's not something that any callers do today as far as I can tell. So I guess it's just expected that callers will not do this. However, it would be useful to know if this happened in future; let's add a warning to cover the eventuality. Signed-off-by: Ryan Roberts Reviewed-by: Anshuman Khandual --- mm/vmalloc.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 61981ee1c9d2..a7e34e6936d2 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -374,8 +374,10 @@ static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, if (cleared || pmd_bad(*pmd)) *mask |= PGTBL_PMD_MODIFIED; - if (cleared) + if (cleared) { + WARN_ON(next - addr < PMD_SIZE); continue; + } if (pmd_none_or_clear_bad(pmd)) continue; vunmap_pte_range(pmd, addr, next, mask); @@ -399,8 +401,10 @@ static void vunmap_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, if (cleared || pud_bad(*pud)) *mask |= PGTBL_PUD_MODIFIED; - if (cleared) + if (cleared) { + WARN_ON(next - addr < PUD_SIZE); continue; + } if (pud_none_or_clear_bad(pud)) continue; vunmap_pmd_range(pud, addr, next, mask);