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Tue, 4 Mar 2025 07:05:08 -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 v3 07/11] mm/vmalloc: Warn on improper use of vunmap_range() Date: Tue, 4 Mar 2025 15:04:37 +0000 Message-ID: <20250304150444.3788920-8-ryan.roberts@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250304150444.3788920-1-ryan.roberts@arm.com> References: <20250304150444.3788920-1-ryan.roberts@arm.com> MIME-Version: 1.0 X-Stat-Signature: jcehzt4xhr7sjgs4s1d6gttdraguafgj X-Rspamd-Queue-Id: BCD19140013 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1741100710-619867 X-HE-Meta: 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 Q2DZ0bBO D9satx8ewd97MFuwsQRlsCfNWduemSXTo7FPrkAIlu5vTIlFTlOe4c4JP2x9eL/AEWaAmwTEiqiVzt1rlHOuCAGaxEVx/8Q7Oo5NyOJG3Pdmcvow+djYxRVjFpw60xCl/yGAWgrMxdJFRVVhKlfYVYIrDLqSotWTQmkDwryccP5V+sJKt+35EglEvpwc2u2aeXFr+KsZHjAfHgD8= 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. Reviewed-by: Anshuman Khandual Reviewed-by: Catalin Marinas Signed-off-by: Ryan Roberts --- mm/vmalloc.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index a6e7acebe9ad..fcdf67d5177a 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);