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Message-ID: <2025050114-CVE-2025-37774-8b9d@gregkh> Date: Thu, 1 May 2025 15:07:22 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...nel.org> Subject: CVE-2025-37774: slab: ensure slab->obj_exts is clear in a newly allocated slab page From: Greg Kroah-Hartman <gregkh@...nel.org> Description =========== In the Linux kernel, the following vulnerability has been resolved: slab: ensure slab->obj_exts is clear in a newly allocated slab page ktest recently reported crashes while running several buffered io tests with __alloc_tagging_slab_alloc_hook() at the top of the crash call stack. The signature indicates an invalid address dereference with low bits of slab->obj_exts being set. The bits were outside of the range used by page_memcg_data_flags and objext_flags and hence were not masked out by slab_obj_exts() when obtaining the pointer stored in slab->obj_exts. The typical crash log looks like this: 00510 Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010 00510 Mem abort info: 00510 ESR = 0x0000000096000045 00510 EC = 0x25: DABT (current EL), IL = 32 bits 00510 SET = 0, FnV = 0 00510 EA = 0, S1PTW = 0 00510 FSC = 0x05: level 1 translation fault 00510 Data abort info: 00510 ISV = 0, ISS = 0x00000045, ISS2 = 0x00000000 00510 CM = 0, WnR = 1, TnD = 0, TagAccess = 0 00510 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 00510 user pgtable: 4k pages, 39-bit VAs, pgdp=0000000104175000 00510 [0000000000000010] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000 00510 Internal error: Oops: 0000000096000045 [#1] SMP 00510 Modules linked in: 00510 CPU: 10 UID: 0 PID: 7692 Comm: cat Not tainted 6.15.0-rc1-ktest-g189e17946605 #19327 NONE 00510 Hardware name: linux,dummy-virt (DT) 00510 pstate: 20001005 (nzCv daif -PAN -UAO -TCO -DIT +SSBS BTYPE=--) 00510 pc : __alloc_tagging_slab_alloc_hook+0xe0/0x190 00510 lr : __kmalloc_noprof+0x150/0x310 00510 sp : ffffff80c87df6c0 00510 x29: ffffff80c87df6c0 x28: 000000000013d1ff x27: 000000000013d200 00510 x26: ffffff80c87df9e0 x25: 0000000000000000 x24: 0000000000000001 00510 x23: ffffffc08041953c x22: 000000000000004c x21: ffffff80c0002180 00510 x20: fffffffec3120840 x19: ffffff80c4821000 x18: 0000000000000000 00510 x17: fffffffec3d02f00 x16: fffffffec3d02e00 x15: fffffffec3d00700 00510 x14: fffffffec3d00600 x13: 0000000000000200 x12: 0000000000000006 00510 x11: ffffffc080bb86c0 x10: 0000000000000000 x9 : ffffffc080201e58 00510 x8 : ffffff80c4821060 x7 : 0000000000000000 x6 : 0000000055555556 00510 x5 : 0000000000000001 x4 : 0000000000000010 x3 : 0000000000000060 00510 x2 : 0000000000000000 x1 : ffffffc080f50cf8 x0 : ffffff80d801d000 00510 Call trace: 00510 __alloc_tagging_slab_alloc_hook+0xe0/0x190 (P) 00510 __kmalloc_noprof+0x150/0x310 00510 __bch2_folio_create+0x5c/0xf8 00510 bch2_folio_create+0x2c/0x40 00510 bch2_readahead+0xc0/0x460 00510 read_pages+0x7c/0x230 00510 page_cache_ra_order+0x244/0x3a8 00510 page_cache_async_ra+0x124/0x170 00510 filemap_readahead.isra.0+0x58/0xa0 00510 filemap_get_pages+0x454/0x7b0 00510 filemap_read+0xdc/0x418 00510 bch2_read_iter+0x100/0x1b0 00510 vfs_read+0x214/0x300 00510 ksys_read+0x6c/0x108 00510 __arm64_sys_read+0x20/0x30 00510 invoke_syscall.constprop.0+0x54/0xe8 00510 do_el0_svc+0x44/0xc8 00510 el0_svc+0x18/0x58 00510 el0t_64_sync_handler+0x104/0x130 00510 el0t_64_sync+0x154/0x158 00510 Code: d5384100 f9401c01 b9401aa3 b40002e1 (f8227881) 00510 ---[ end trace 0000000000000000 ]--- 00510 Kernel panic - not syncing: Oops: Fatal exception 00510 SMP: stopping secondary CPUs 00510 Kernel Offset: disabled 00510 CPU features: 0x0000,000000e0,00000410,8240500b 00510 Memory Limit: none Investigation indicates that these bits are already set when we allocate slab page and are not zeroed out after allocation. We are not yet sure why these crashes start happening only recently but regardless of the reason, not initializing a field that gets used later is wrong. Fix it by initializing slab->obj_exts during slab page allocation. The Linux kernel CVE team has assigned CVE-2025-37774 to this issue. Affected and fixed versions =========================== Issue introduced in 6.10 with commit 21c690a349baab895dc68ab70d291e1598d7109d and fixed in 6.12.25 with commit 8baa747193591410a853bac9c3710142dfa4937b Issue introduced in 6.10 with commit 21c690a349baab895dc68ab70d291e1598d7109d and fixed in 6.14.4 with commit 28bef6622a1a874fe63aceeb0c684fab75afb3ae Issue introduced in 6.10 with commit 21c690a349baab895dc68ab70d291e1598d7109d and fixed in 6.15-rc3 with commit d2f5819b6ed357c0c350c0616b6b9f38be59adf6 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2025-37774 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: mm/slub.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/8baa747193591410a853bac9c3710142dfa4937b https://git.kernel.org/stable/c/28bef6622a1a874fe63aceeb0c684fab75afb3ae https://git.kernel.org/stable/c/d2f5819b6ed357c0c350c0616b6b9f38be59adf6
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