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Mon, 4 Aug 2025 15:19:59 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id KmCHOp/PkGiscwAAD6G6ig (envelope-from ); Mon, 04 Aug 2025 15:19:59 +0000 Message-ID: Date: Mon, 4 Aug 2025 17:19:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6] mm/slub: avoid accessing metadata when pointer is invalid in object_err() Content-Language: en-US To: Li Qiong , Christoph Lameter , David Rientjes , Andrew Morton Cc: Roman Gushchin , Harry Yoo , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Matthew Wilcox References: <20250804025759.382343-1-liqiong@nfschina.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <20250804025759.382343-1-liqiong@nfschina.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C1AF840006 X-Stat-Signature: dn74b19ezxaam999aum3pzg4xye1jy4n X-HE-Tag: 1754320801-819615 X-HE-Meta: U2FsdGVkX18rBGZuAy2w23LRSXjorfFOvXk2RHECeMhIQHKiry71TTNB0ou0cf8T2u7+v6f0TlVblVIvHN9l2MJzHYL4RkKXx58luGG3RcUJ6vS0IyvYqIFgOyBc2QKcBQjrc8wVrNwT4qjpYpF5iTyTo2wcTzgMjkJlI+wNJzat4yeJGoerdFBKbcdxFkIKoUlwGT85F5sY1VrBfNt9yrN8pBNEsQsQCuVn+yCb/8bEAzK5FYb0WhJugzmUBqVXf5fn5d2KMydsBEvr74cxWJvmRu4XpspkCJ+O3Vu3VVkGaa3Xj71nmBfT2aBmZqjYOLH4E3/SwasYtQcZ5P5cwjbk2Sw4vkXyv2L6ztmPJadlSz37lIypCbLJMFK6LmdRNe89wucRpLwYvlYAl1KjFvGDPZZAoYjyorLIB4mTmW3hxg5Q0gOqbKOcPiOMgc/Gp5y0/Mb4V1Eix9wnX2kH7FsvNLBd/YD0Cp9PFExNU8YL4HAo6KhLHhJF8Mxd0vtndW7oiiRHcBMJKJCi/BGowZsXS5yAPJNePitSt00uaKkwZmWPhvg7KsXpim6WeBBAdXBx+/kO5xvOy1D+kR6/S08BAMBLkx/j4Jm7qFDEIvfuWB6/fK0hpejYhGj1zb+PkIwE34O1Zkb1k5HnOBOjyUjxEjjNit9s4gQAWwggfnUVY/wC/fF6hzdMOMC0vB4DGPqbJIOX9YGKBytHX+C+oDayuqyTzsCD1oTeyGiEOykUAIxsGletUzgQk8HfYLGTtIrQsFzet0ft11sp7rL5GlPiJDJ1DYSgwFTaDDUL09359pBooafIjcGk+/sCCnRG85JT5DRGWGWDeh6TiVo2bhcH1pmRyyice1NfU0ArDo4bLyLkmtQ39/cVFQn3tYpWh/ki31DWc2LzHl6m7RcNJxbpIRmcWWFaePzUJB86V2OK8CMrg+EUN4MN7XEZPZI30JkZc/aWP7cSToqDtKC 4f4olxym xENUGWE05tYuq0nUOirZhSiYEcFrQ+9odYKSovwbkPuWkbgxWj2YTm0Mn1f9OV9H+ZOr3xMxML7i03t4yOr8lxkadWg4np16gc7LLYpXmhZn8H2cPgdXV7b61b0/Bip5X3LUIc7Zb6QEFtbmiVQ4FUuTiTSH4H3H2REHHMO5CmdZ46vpL3vUPxJD7bV4refpVUe6uUJA77Opg514SL0b45TEH3Vl6FTcrIYSDbK7kCLngDX6od//jnDzCq38vvT+1s8GMyYnYfcf+735cnf84xT0LkX67BNmN46eOJ41dFCyjF6Qyen/h0rDdBjCFm98uI3cKf3SnQiSO46DQsHVtPvCdRddReUDI3YKR7TVcxDL/YDfobc8tbb+YFAVNdUHvZ58e 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: On 8/4/25 04:57, Li Qiong wrote: > object_err() reports details of an object for further debugging, such as > the freelist pointer, redzone, etc. However, if the pointer is invalid, > attempting to access object metadata can lead to a crash since it does > not point to a valid object. > > In case the pointer is NULL or check_valid_pointer() returns false for > the pointer, only print the pointer value and skip accessing metadata. We should explain that this is not theoretical so justify the stable cc, so I would add: One known path to the crash is when alloc_consistency_checks() determines the pointer to the allocated object is invalid beause of a freelist corruption, and calls object_err() to report it. The debug code should report and handle the corruption gracefully and not crash in the process. If you agree, I can do this when picking up the patch after merge window, no need to resend. > Fixes: 81819f0fc828 ("SLUB core") > Cc: > Signed-off-by: Li Qiong > --- > v2: > - rephrase the commit message, add comment for object_err(). > v3: > - check object pointer in object_err(). > v4: > - restore changes in alloc_consistency_checks(). > v5: > - rephrase message, fix code style. > v6: > - add checking 'object' if NULL. > --- > mm/slub.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 31e11ef256f9..972cf2bb2ee6 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -1104,7 +1104,12 @@ static void object_err(struct kmem_cache *s, struct slab *slab, > return; > > slab_bug(s, reason); > - print_trailer(s, slab, object); > + if (!object || !check_valid_pointer(s, slab, object)) { > + print_slab_info(slab); > + pr_err("Invalid pointer 0x%p\n", object); > + } else { > + print_trailer(s, slab, object); > + } > add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); > > WARN_ON(1);