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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?v/6hvJFrV6TUub27uC5RkoIKlT15snVPWtegKouxg7InMuBStd2LmgMpXH31?= =?us-ascii?Q?D+V1DcvfRDSpdcAa7ShUwxQzBX1vm3oL0QRfSEsG/WP2pXaWWDE7Vh1yJXI+?= =?us-ascii?Q?Ki8gxo6rgSVp1bJMvPaMQCiGxdnkG2wTZ9eTMryWCRgbyGh/rk286AZEf0yc?= =?us-ascii?Q?zKgZ7dGoZRbesAed7lQX7JF8SGnPVEd5li7lqC8pbd8ZEPALWGdj0zF75Abp?= =?us-ascii?Q?pZmM0u/joscnAbMj3Gau5mAjFKS6lFLzu8dcwk5ojy1XuV96IYqwJBpFr7jT?= =?us-ascii?Q?wvuFW8jjo5w1olXywza6EQ0SRJSxcHscdLiPBkBSlofAZLGMDEqpfnz+3sMv?= =?us-ascii?Q?kJ8wle51lNmmb34xM6bur2vi4/mOz1866vd3xWB4nPivL542aMQgJ7hzYmnc?= =?us-ascii?Q?k9H3/L+Z7+KZdmzcWtIViYnZnxUOEP9PcZSHKD+3zhH2sInWW+XK4s6cR5lN?= =?us-ascii?Q?Jlpok9W//rud1qKofUjm4qMHlBd6M5mHGIvfZHlDwvuv0c2Cb3h54bCCy4qR?= =?us-ascii?Q?T1TIid3jlxsFqPtG8TrjX83mbAeQnWyz1siKN/0lulAuecPutJAQGnD8UmPP?= =?us-ascii?Q?7kURpgeuHwXGbI2Azb9+G8+TlO5mSX2yhsHpk649Z83dtmbu0tGO+wMegDvd?= =?us-ascii?Q?you8sxjk4Kp00ahlH9/J3Xh0uZ2b1SkrqGQXcWx+yYZFFjkchVuFVhcOvaQz?= =?us-ascii?Q?fOoN2kT/AxZrWWIxjgmMH2qMoVYuDTNloxLhbYIMgXGXSOoZ0stq6IUHFjNG?= =?us-ascii?Q?LUStDiO2Rnd1okfwkDdKzwD4XG2rTEFu2jDeqlDB3jMjmeA2D1QWl3oywCUH?= =?us-ascii?Q?YOmT8Hs7iipTj55UlPFdenB+/vPo3cZLQADwhAJ8CRuZQ427Tb2TGvznzILf?= =?us-ascii?Q?5yy9O5kE68qL9BvLfnVR9UVZ97E8R4jGdNVz0kPx+TX5hxqJAEJrvfpNsYN9?= =?us-ascii?Q?Wy68vGNJVYXM/RIzssE4rCxxAYnW0ag7B6AV9FVzD3J2wKzuVWcsrLN+Qrtu?= =?us-ascii?Q?BcLY299RL9qsnf2BAOqTAsN26a5y6j1+Dp/li0z9w4fWQL6K7ruIF4RHojYh?= =?us-ascii?Q?yuQFpkpUB+3/SWm14ZXfcz2qpgtpk+/WmY05Sfl+3+fBtceq0LNeqBnWrncB?= =?us-ascii?Q?OeoghOHKe+bsqLLE75AlTwodht4bwwHmnN0yI9MgFzvh5M3Ag0jgqD5L0E4F?= =?us-ascii?Q?QyMqHxRAe2mResjcthiKLNEaFxNOpkfYpCUWUWv0L1B0U7uJjAkgogs/6VoQ?= =?us-ascii?Q?rGl95U2mHe16x15mKfCg7GCA1IsScWd1WAfhKqpsSZOxZ8vQvbLYqtRNLB5S?= =?us-ascii?Q?X6YWmrNaL0NRAKv8aJCDjnVqrlRP1/VlxaMv9aKM4ES72Lbt+nLNgFERNgOC?= =?us-ascii?Q?Y+MRu+DiAmg9+OYL8sSIYL9W/BUzCj7ryp8bxrON8Wt6tf/o7v1DLrxSOIU4?= =?us-ascii?Q?lk0vH2CeTM9JNZRDsrIK45E1aMK48IItvoqj/4N45WrJqF6AMCswNZa0MyWC?= =?us-ascii?Q?lmpnH510o1w5k7mBKLQIbBySmzMTtEGzdl0YMRVQ7gmbwko1pIE6e55uxo8J?= =?us-ascii?Q?uCdt40TKo6MmNI8G+RjeYBeo4vIIttZscAtlrskNXInN4jcuZ8iPA+IboSQm?= =?us-ascii?Q?t/WWetNPPYSLFlMXiM6bLuStL3Grd7+yVuaiKhDJW1HZQezAYSexZRog9iYb?= =?us-ascii?Q?E07JCI6xm6WWzHcJmDHgR/ZVPr8H8WjW6GxZAIZ3LsVFPUuaBRiIB12R5n+e?= =?us-ascii?Q?uLTfSelX3A=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: eec2ef35-8434-4b3e-49c3-08defc8fb0da X-MS-Exchange-CrossTenant-AuthSource: IA0PR12MB8374.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Aug 2026 18:45:21.2500 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: v7rVCNOWtdhVk67iSjivZBgnvNxI3KMLifwfmK6emUe6m9GTxyjkliVJfPsMK4/G X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB7529 On 17 Aug 2026, at 11:37, Alan Stern wrote: > On Mon, Aug 17, 2026 at 11:22:47AM -0400, Zi Yan wrote: >>> Again, I disagree with some of the details of this argument in this >>> context. For instance, if all kernel developers are supposed to know= >>> that they shouldn't ask kmalloc() for more than MAX_PAGE_ORDER at the= >>> risk of provoking a WARN, if this is such an important restriction, t= hen >>> shouldn't this requirement be mentioned in the kerneldoc for kmalloc(= )? >> >> >> kmalloc is the normal method of allocating memory >> for objects smaller than page size in the kernel. > > This means when you are allocating small objects, kmalloc is the normal= > way to do it. It says nothing about what you should do when allocating= > large objects. alloc_pages() or vmalloc or kvmalloc(). kmalloc() is used if you really want physically contiguous memory. > > In particular, it doesn't say that if you ask kmalloc for more than 4 M= B > of memory, your system is likely to crash. Crash because panic_on_warn is set. You just conflate a sysctl config wit= h a WARN. I understand panic_on_warn is set by many systems, but that does = not mean every system crashes. Plus, if you use kvmalloc with a really large size, you also can get a WARN[1][2]. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tr= ee/mm/slub.c?h=3Dv7.2#n6912 [2] https://lore.kernel.org/all/CAHk-=3DwiRq+_jd_O1gz3J6-ANtXMY7iLpi8XFUc= mtB3rBixvUXQ@mail.gmail.com/ > >> See https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git= /tree/include/linux/slab.h?h=3Dv7.2#n1001 >> >> In this case, kmalloc is used to request > 4MB memory. >> >>> >>> Regardless, if it is important to let kernel developers know that the= ir >>> code is doing something wrong, why not make the WARN conditional on >>> CONFIG_EXPERT or something similar? In other words, prevent it from >>> crashing production systems. > > You didn't respond to this. I do not get your argument here. Why does this WARN need to be conditiona= l on CONFIG_EXPERT? What makes it special? Or you mean you want all WARNs to be conditional CONFIG_EXPERT? Anyway, if you do not want to check user input len and want core MM to do the check. I will send a patch to make kmalloc return NULL when the requested len is bigger than KMALLOC_MAX_SIZE without giving a warnin= g, based on my discussion with Vlastimil on IRC (he is out until next week).= Best Regards, Yan, Zi