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Tue, 14 Apr 2026 11:13:23 +0000 (GMT) Message-ID: Date: Tue, 14 Apr 2026 16:43:21 +0530 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/memblock: fix off-by-one page leak in reserve_mem_release_by_name() To: DaeMyung Kang , Mike Rapoport , Andrew Morton Cc: Masami Hiramatsu , Steven Rostedt , stable@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260414094439.982853-1-charsyam@gmail.com> <20260414104353.989063-1-charsyam@gmail.com> Content-Language: en-US From: Donet Tom In-Reply-To: <20260414104353.989063-1-charsyam@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: wkLhB1sG-uScmjyYMpuqjEOmKu6tMIPb X-Proofpoint-ORIG-GUID: 7JcEVzdBO7YccUBjh6yMYYB6HFHeu3pv X-Authority-Analysis: v=2.4 cv=WbE8rUhX c=1 sm=1 tr=0 ts=69de2158 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VwQbUJbxAAAA:8 a=pGLkceISAAAA:8 a=VnNF1IyMAAAA:8 a=A9Q-lSG_ta5snbpTm5QA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDE0MDEwMSBTYWx0ZWRfX3M/DsbIwZE4i QAWM4kkD8F/DarLEXqCHMCquT2f/UVJ7m+ub+kBtazP1cOwUOIJTAsIOXzjPzwrWJr+wlFgqaK5 zprW8W8enLD+5lQUXdOgnxxwrnDzcrpLK16CaqzBVOKAOVYqRrZrMyQTFDMk1L/arC82TyUhlXu OpSY9WCcLjihggUiuQYfjXo/QEZ2nQV84Nbyzzrhttlwn/FVi24h4giwqqGePAys21GhXCPyhaP JDDrUo5U7YWwTOKV/sDidYh6vmiIm6n1uwemOKXMa/sGn1zpsw6FqAx9lPfUO3Hvjra+YAD8f+B LlJHkNE/ZsvpFkdoL0tc2xgumxR0tZa0xnD0R2KeJVnMhUSca+as1Ycd1Bq63ECeR4iDwB2PlpR GHZ5H927brRWyFnpnqbgR0DBGr6XLzRkjksaj82OWTKKy+Twy/nVpQXELBM/OH9PVVFBpZgpwEh g3JrLg7FykuytS6jdAQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-14_02,2026-04-13_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 bulkscore=0 priorityscore=1501 spamscore=0 clxscore=1011 phishscore=0 impostorscore=0 adultscore=0 malwarescore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604070000 definitions=main-2604140101 Hi On 4/14/26 4:13 PM, DaeMyung Kang wrote: > free_reserved_area() treats its 'end' argument as exclusive: it aligns > end down via 'end & PAGE_MASK' and iterates with 'pos < end'. > > reserve_mem_release_by_name() instead passes 'start + map->size - 1', > which causes the last page of a page-aligned reservation to never be > freed. For a reservation spanning N pages, only N - 1 pages are > released back to the allocator. > > Fix it by passing the exclusive end address, 'start + map->size'. > > Fixes: 74e2498ccf7b ("mm/memblock: Add reserved memory release function") > Cc: stable@vger.kernel.org > Signed-off-by: DaeMyung Kang I think it might be better to send v2 as a separate patch  rather than as a reply to the previous version. This patch looks good to me. Reviewed-by: Donet Tom donettom@linux.ibm.com -Donet > --- > Changes in v2: > - Add Fixes: tag and Cc: stable (per Donet Tom's review). > - v1: https://lore.kernel.org/lkml/ > > mm/memblock.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memblock.c b/mm/memblock.c > index b3ddfdec7a80..d4a02f1750e9 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -2434,7 +2434,7 @@ int reserve_mem_release_by_name(const char *name) > return 0; > > start = phys_to_virt(map->start); > - end = start + map->size - 1; > + end = start + map->size; > snprintf(buf, sizeof(buf), "reserve_mem:%s", name); > free_reserved_area(start, end, 0, buf); > map->size = 0;