Filtered by CWE-121
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Total 2118 CVE
CVE Vendors Products Updated CVSS v3.1
CVE-2024-26883 1 Linux 1 Linux Kernel 2024-12-19 7.8 High
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix stackmap overflow check on 32-bit arches The stackmap code relies on roundup_pow_of_two() to compute the number of hash buckets, and contains an overflow check by checking if the resulting value is 0. However, on 32-bit arches, the roundup code itself can overflow by doing a 32-bit left-shift of an unsigned long value, which is undefined behaviour, so it is not guaranteed to truncate neatly. This was triggered by syzbot on the DEVMAP_HASH type, which contains the same check, copied from the hashtab code. The commit in the fixes tag actually attempted to fix this, but the fix did not account for the UB, so the fix only works on CPUs where an overflow does result in a neat truncation to zero, which is not guaranteed. Checking the value before rounding does not have this problem.
CVE-2024-26843 1 Redhat 1 Enterprise Linux 2024-12-19 6 Medium
In the Linux kernel, the following vulnerability has been resolved: efi: runtime: Fix potential overflow of soft-reserved region size md_size will have been narrowed if we have >= 4GB worth of pages in a soft-reserved region.
CVE-2024-26768 2024-12-19 6.5 Medium
In the Linux kernel, the following vulnerability has been resolved: LoongArch: Change acpi_core_pic[NR_CPUS] to acpi_core_pic[MAX_CORE_PIC] With default config, the value of NR_CPUS is 64. When HW platform has more then 64 cpus, system will crash on these platforms. MAX_CORE_PIC is the maximum cpu number in MADT table (max physical number) which can exceed the supported maximum cpu number (NR_CPUS, max logical number), but kernel should not crash. Kernel should boot cpus with NR_CPUS, let the remainder cpus stay in BIOS. The potential crash reason is that the array acpi_core_pic[NR_CPUS] can be overflowed when parsing MADT table, and it is obvious that CORE_PIC should be corresponding to physical core rather than logical core, so it is better to define the array as acpi_core_pic[MAX_CORE_PIC]. With the patch, system can boot up 64 vcpus with qemu parameter -smp 128, otherwise system will crash with the following message. [ 0.000000] CPU 0 Unable to handle kernel paging request at virtual address 0000420000004259, era == 90000000037a5f0c, ra == 90000000037a46ec [ 0.000000] Oops[#1]: [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 6.8.0-rc2+ #192 [ 0.000000] Hardware name: QEMU QEMU Virtual Machine, BIOS unknown 2/2/2022 [ 0.000000] pc 90000000037a5f0c ra 90000000037a46ec tp 9000000003c90000 sp 9000000003c93d60 [ 0.000000] a0 0000000000000019 a1 9000000003d93bc0 a2 0000000000000000 a3 9000000003c93bd8 [ 0.000000] a4 9000000003c93a74 a5 9000000083c93a67 a6 9000000003c938f0 a7 0000000000000005 [ 0.000000] t0 0000420000004201 t1 0000000000000000 t2 0000000000000001 t3 0000000000000001 [ 0.000000] t4 0000000000000003 t5 0000000000000000 t6 0000000000000030 t7 0000000000000063 [ 0.000000] t8 0000000000000014 u0 ffffffffffffffff s9 0000000000000000 s0 9000000003caee98 [ 0.000000] s1 90000000041b0480 s2 9000000003c93da0 s3 9000000003c93d98 s4 9000000003c93d90 [ 0.000000] s5 9000000003caa000 s6 000000000a7fd000 s7 000000000f556b60 s8 000000000e0a4330 [ 0.000000] ra: 90000000037a46ec platform_init+0x214/0x250 [ 0.000000] ERA: 90000000037a5f0c efi_runtime_init+0x30/0x94 [ 0.000000] CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE) [ 0.000000] PRMD: 00000000 (PPLV0 -PIE -PWE) [ 0.000000] EUEN: 00000000 (-FPE -SXE -ASXE -BTE) [ 0.000000] ECFG: 00070800 (LIE=11 VS=7) [ 0.000000] ESTAT: 00010000 [PIL] (IS= ECode=1 EsubCode=0) [ 0.000000] BADV: 0000420000004259 [ 0.000000] PRID: 0014c010 (Loongson-64bit, Loongson-3A5000) [ 0.000000] Modules linked in: [ 0.000000] Process swapper (pid: 0, threadinfo=(____ptrval____), task=(____ptrval____)) [ 0.000000] Stack : 9000000003c93a14 9000000003800898 90000000041844f8 90000000037a46ec [ 0.000000] 000000000a7fd000 0000000008290000 0000000000000000 0000000000000000 [ 0.000000] 0000000000000000 0000000000000000 00000000019d8000 000000000f556b60 [ 0.000000] 000000000a7fd000 000000000f556b08 9000000003ca7700 9000000003800000 [ 0.000000] 9000000003c93e50 9000000003800898 9000000003800108 90000000037a484c [ 0.000000] 000000000e0a4330 000000000f556b60 000000000a7fd000 000000000f556b08 [ 0.000000] 9000000003ca7700 9000000004184000 0000000000200000 000000000e02b018 [ 0.000000] 000000000a7fd000 90000000037a0790 9000000003800108 0000000000000000 [ 0.000000] 0000000000000000 000000000e0a4330 000000000f556b60 000000000a7fd000 [ 0.000000] 000000000f556b08 000000000eaae298 000000000eaa5040 0000000000200000 [ 0.000000] ... [ 0.000000] Call Trace: [ 0.000000] [<90000000037a5f0c>] efi_runtime_init+0x30/0x94 [ 0.000000] [<90000000037a46ec>] platform_init+0x214/0x250 [ 0.000000] [<90000000037a484c>] setup_arch+0x124/0x45c [ 0.000000] [<90000000037a0790>] start_kernel+0x90/0x670 [ 0.000000] [<900000000378b0d8>] kernel_entry+0xd8/0xdc
CVE-2024-26753 2024-12-19 6.0 Medium
In the Linux kernel, the following vulnerability has been resolved: crypto: virtio/akcipher - Fix stack overflow on memcpy sizeof(struct virtio_crypto_akcipher_session_para) is less than sizeof(struct virtio_crypto_op_ctrl_req::u), copying more bytes from stack variable leads stack overflow. Clang reports this issue by commands: make -j CC=clang-14 mrproper >/dev/null 2>&1 make -j O=/tmp/crypto-build CC=clang-14 allmodconfig >/dev/null 2>&1 make -j O=/tmp/crypto-build W=1 CC=clang-14 drivers/crypto/virtio/ virtio_crypto_akcipher_algs.o
CVE-2024-26736 2024-12-19 4.7 Medium
In the Linux kernel, the following vulnerability has been resolved: afs: Increase buffer size in afs_update_volume_status() The max length of volume->vid value is 20 characters. So increase idbuf[] size up to 24 to avoid overflow. Found by Linux Verification Center (linuxtesting.org) with SVACE. [DH: Actually, it's 20 + NUL, so increase it to 24 and use snprintf()]
CVE-2024-26710 2024-12-19 4.4 Medium
In the Linux kernel, the following vulnerability has been resolved: powerpc/kasan: Limit KASAN thread size increase to 32KB KASAN is seen to increase stack usage, to the point that it was reported to lead to stack overflow on some 32-bit machines (see link). To avoid overflows the stack size was doubled for KASAN builds in commit 3e8635fb2e07 ("powerpc/kasan: Force thread size increase with KASAN"). However with a 32KB stack size to begin with, the doubling leads to a 64KB stack, which causes build errors: arch/powerpc/kernel/switch.S:249: Error: operand out of range (0x000000000000fe50 is not between 0xffffffffffff8000 and 0x0000000000007fff) Although the asm could be reworked, in practice a 32KB stack seems sufficient even for KASAN builds - the additional usage seems to be in the 2-3KB range for a 64-bit KASAN build. So only increase the stack for KASAN if the stack size is < 32KB.
CVE-2023-52796 1 Redhat 1 Enterprise Linux 2024-12-19 4.4 Medium
In the Linux kernel, the following vulnerability has been resolved: ipvlan: add ipvlan_route_v6_outbound() helper Inspired by syzbot reports using a stack of multiple ipvlan devices. Reduce stack size needed in ipvlan_process_v6_outbound() by moving the flowi6 struct used for the route lookup in an non inlined helper. ipvlan_route_v6_outbound() needs 120 bytes on the stack, immediately reclaimed. Also make sure ipvlan_process_v4_outbound() is not inlined. We might also have to lower MAX_NEST_DEV, because only syzbot uses setups with more than four stacked devices. BUG: TASK stack guard page was hit at ffffc9000e803ff8 (stack is ffffc9000e804000..ffffc9000e808000) stack guard page: 0000 [#1] SMP KASAN CPU: 0 PID: 13442 Comm: syz-executor.4 Not tainted 6.1.52-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 RIP: 0010:kasan_check_range+0x4/0x2a0 mm/kasan/generic.c:188 Code: 48 01 c6 48 89 c7 e8 db 4e c1 03 31 c0 5d c3 cc 0f 0b eb 02 0f 0b b8 ea ff ff ff 5d c3 cc 00 00 cc cc 00 00 cc cc 55 48 89 e5 <41> 57 41 56 41 55 41 54 53 b0 01 48 85 f6 0f 84 a4 01 00 00 48 89 RSP: 0018:ffffc9000e804000 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817e5bf2 RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff887c6568 RBP: ffffc9000e804000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff92001d0080c R13: dffffc0000000000 R14: ffffffff87e6b100 R15: 0000000000000000 FS: 00007fd0c55826c0(0000) GS:ffff8881f6800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffc9000e803ff8 CR3: 0000000170ef7000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <#DF> </#DF> <TASK> [<ffffffff81f281d1>] __kasan_check_read+0x11/0x20 mm/kasan/shadow.c:31 [<ffffffff817e5bf2>] instrument_atomic_read include/linux/instrumented.h:72 [inline] [<ffffffff817e5bf2>] _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] [<ffffffff817e5bf2>] cpumask_test_cpu include/linux/cpumask.h:506 [inline] [<ffffffff817e5bf2>] cpu_online include/linux/cpumask.h:1092 [inline] [<ffffffff817e5bf2>] trace_lock_acquire include/trace/events/lock.h:24 [inline] [<ffffffff817e5bf2>] lock_acquire+0xe2/0x590 kernel/locking/lockdep.c:5632 [<ffffffff8563221e>] rcu_lock_acquire+0x2e/0x40 include/linux/rcupdate.h:306 [<ffffffff8561464d>] rcu_read_lock include/linux/rcupdate.h:747 [inline] [<ffffffff8561464d>] ip6_pol_route+0x15d/0x1440 net/ipv6/route.c:2221 [<ffffffff85618120>] ip6_pol_route_output+0x50/0x80 net/ipv6/route.c:2606 [<ffffffff856f65b5>] pol_lookup_func include/net/ip6_fib.h:584 [inline] [<ffffffff856f65b5>] fib6_rule_lookup+0x265/0x620 net/ipv6/fib6_rules.c:116 [<ffffffff85618009>] ip6_route_output_flags_noref+0x2d9/0x3a0 net/ipv6/route.c:2638 [<ffffffff8561821a>] ip6_route_output_flags+0xca/0x340 net/ipv6/route.c:2651 [<ffffffff838bd5a3>] ip6_route_output include/net/ip6_route.h:100 [inline] [<ffffffff838bd5a3>] ipvlan_process_v6_outbound drivers/net/ipvlan/ipvlan_core.c:473 [inline] [<ffffffff838bd5a3>] ipvlan_process_outbound drivers/net/ipvlan/ipvlan_core.c:529 [inline] [<ffffffff838bd5a3>] ipvlan_xmit_mode_l3 drivers/net/ipvlan/ipvlan_core.c:602 [inline] [<ffffffff838bd5a3>] ipvlan_queue_xmit+0xc33/0x1be0 drivers/net/ipvlan/ipvlan_core.c:677 [<ffffffff838c2909>] ipvlan_start_xmit+0x49/0x100 drivers/net/ipvlan/ipvlan_main.c:229 [<ffffffff84d03900>] netdev_start_xmit include/linux/netdevice.h:4966 [inline] [<ffffffff84d03900>] xmit_one net/core/dev.c:3644 [inline] [<ffffffff84d03900>] dev_hard_start_xmit+0x320/0x980 net/core/dev.c:3660 [<ffffffff84d080e2>] __dev_queue_xmit+0x16b2/0x3370 net/core/dev.c:4324 [<ffffffff855ce4cd>] dev_queue_xmit include/linux/netdevice.h:3067 [inline] [<ffffffff855ce4cd>] neigh_hh_output include/net/neighbour.h:529 [inline] [<f ---truncated---
CVE-2023-52762 1 Redhat 1 Enterprise Linux 2024-12-19 5.5 Medium
In the Linux kernel, the following vulnerability has been resolved: virtio-blk: fix implicit overflow on virtio_max_dma_size The following codes have an implicit conversion from size_t to u32: (u32)max_size = (size_t)virtio_max_dma_size(vdev); This may lead overflow, Ex (size_t)4G -> (u32)0. Once virtio_max_dma_size() has a larger size than U32_MAX, use U32_MAX instead.
CVE-2023-52761 2024-12-19 4.4 Medium
In the Linux kernel, the following vulnerability has been resolved: riscv: VMAP_STACK overflow detection thread-safe commit 31da94c25aea ("riscv: add VMAP_STACK overflow detection") added support for CONFIG_VMAP_STACK. If overflow is detected, CPU switches to `shadow_stack` temporarily before switching finally to per-cpu `overflow_stack`. If two CPUs/harts are racing and end up in over flowing kernel stack, one or both will end up corrupting each other state because `shadow_stack` is not per-cpu. This patch optimizes per-cpu overflow stack switch by directly picking per-cpu `overflow_stack` and gets rid of `shadow_stack`. Following are the changes in this patch - Defines an asm macro to obtain per-cpu symbols in destination register. - In entry.S, when overflow is detected, per-cpu overflow stack is located using per-cpu asm macro. Computing per-cpu symbol requires a temporary register. x31 is saved away into CSR_SCRATCH (CSR_SCRATCH is anyways zero since we're in kernel). Please see Links for additional relevant disccussion and alternative solution. Tested by `echo EXHAUST_STACK > /sys/kernel/debug/provoke-crash/DIRECT` Kernel crash log below Insufficient stack space to handle exception!/debug/provoke-crash/DIRECT Task stack: [0xff20000010a98000..0xff20000010a9c000] Overflow stack: [0xff600001f7d98370..0xff600001f7d99370] CPU: 1 PID: 205 Comm: bash Not tainted 6.1.0-rc2-00001-g328a1f96f7b9 #34 Hardware name: riscv-virtio,qemu (DT) epc : __memset+0x60/0xfc ra : recursive_loop+0x48/0xc6 [lkdtm] epc : ffffffff808de0e4 ra : ffffffff0163a752 sp : ff20000010a97e80 gp : ffffffff815c0330 tp : ff600000820ea280 t0 : ff20000010a97e88 t1 : 000000000000002e t2 : 3233206874706564 s0 : ff20000010a982b0 s1 : 0000000000000012 a0 : ff20000010a97e88 a1 : 0000000000000000 a2 : 0000000000000400 a3 : ff20000010a98288 a4 : 0000000000000000 a5 : 0000000000000000 a6 : fffffffffffe43f0 a7 : 00007fffffffffff s2 : ff20000010a97e88 s3 : ffffffff01644680 s4 : ff20000010a9be90 s5 : ff600000842ba6c0 s6 : 00aaaaaac29e42b0 s7 : 00fffffff0aa3684 s8 : 00aaaaaac2978040 s9 : 0000000000000065 s10: 00ffffff8a7cad10 s11: 00ffffff8a76a4e0 t3 : ffffffff815dbaf4 t4 : ffffffff815dbaf4 t5 : ffffffff815dbab8 t6 : ff20000010a9bb48 status: 0000000200000120 badaddr: ff20000010a97e88 cause: 000000000000000f Kernel panic - not syncing: Kernel stack overflow CPU: 1 PID: 205 Comm: bash Not tainted 6.1.0-rc2-00001-g328a1f96f7b9 #34 Hardware name: riscv-virtio,qemu (DT) Call Trace: [<ffffffff80006754>] dump_backtrace+0x30/0x38 [<ffffffff808de798>] show_stack+0x40/0x4c [<ffffffff808ea2a8>] dump_stack_lvl+0x44/0x5c [<ffffffff808ea2d8>] dump_stack+0x18/0x20 [<ffffffff808dec06>] panic+0x126/0x2fe [<ffffffff800065ea>] walk_stackframe+0x0/0xf0 [<ffffffff0163a752>] recursive_loop+0x48/0xc6 [lkdtm] SMP: stopping secondary CPUs ---[ end Kernel panic - not syncing: Kernel stack overflow ]---
CVE-2023-52748 2024-12-19 5.5 Medium
In the Linux kernel, the following vulnerability has been resolved: f2fs: avoid format-overflow warning With gcc and W=1 option, there's a warning like this: fs/f2fs/compress.c: In function ‘f2fs_init_page_array_cache’: fs/f2fs/compress.c:1984:47: error: ‘%u’ directive writing between 1 and 7 bytes into a region of size between 5 and 8 [-Werror=format-overflow=] 1984 | sprintf(slab_name, "f2fs_page_array_entry-%u:%u", MAJOR(dev), MINOR(dev)); | ^~ String "f2fs_page_array_entry-%u:%u" can up to 35. The first "%u" can up to 4 and the second "%u" can up to 7, so total size is "24 + 4 + 7 = 35". slab_name's size should be 35 rather than 32.
CVE-2023-52735 2 Linux, Redhat 2 Linux Kernel, Rhel Eus 2024-12-19 9.1 Critical
In the Linux kernel, the following vulnerability has been resolved: bpf, sockmap: Don't let sock_map_{close,destroy,unhash} call itself sock_map proto callbacks should never call themselves by design. Protect against bugs like [1] and break out of the recursive loop to avoid a stack overflow in favor of a resource leak. [1] https://lore.kernel.org/all/[email protected]/
CVE-2023-52733 1 Linux 1 Linux Kernel 2024-12-19 7.8 High
In the Linux kernel, the following vulnerability has been resolved: s390/decompressor: specify __decompress() buf len to avoid overflow Historically calls to __decompress() didn't specify "out_len" parameter on many architectures including s390, expecting that no writes beyond uncompressed kernel image are performed. This has changed since commit 2aa14b1ab2c4 ("zstd: import usptream v1.5.2") which includes zstd library commit 6a7ede3dfccb ("Reduce size of dctx by reutilizing dst buffer (#2751)"). Now zstd decompression code might store literal buffer in the unwritten portion of the destination buffer. Since "out_len" is not set, it is considered to be unlimited and hence free to use for optimization needs. On s390 this might corrupt initrd or ipl report which are often placed right after the decompressor buffer. Luckily the size of uncompressed kernel image is already known to the decompressor, so to avoid the problem simply specify it in the "out_len" parameter.
CVE-2023-52618 2024-12-19 5.3 Medium
In the Linux kernel, the following vulnerability has been resolved: block/rnbd-srv: Check for unlikely string overflow Since "dev_search_path" can technically be as large as PATH_MAX, there was a risk of truncation when copying it and a second string into "full_path" since it was also PATH_MAX sized. The W=1 builds were reporting this warning: drivers/block/rnbd/rnbd-srv.c: In function 'process_msg_open.isra': drivers/block/rnbd/rnbd-srv.c:616:51: warning: '%s' directive output may be truncated writing up to 254 bytes into a region of size between 0 and 4095 [-Wformat-truncation=] 616 | snprintf(full_path, PATH_MAX, "%s/%s", | ^~ In function 'rnbd_srv_get_full_path', inlined from 'process_msg_open.isra' at drivers/block/rnbd/rnbd-srv.c:721:14: drivers/block/rnbd/rnbd-srv.c:616:17: note: 'snprintf' output between 2 and 4351 bytes into a destination of size 4096 616 | snprintf(full_path, PATH_MAX, "%s/%s", | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 617 | dev_search_path, dev_name); | ~~~~~~~~~~~~~~~~~~~~~~~~~~ To fix this, unconditionally check for truncation (as was already done for the case where "%SESSNAME%" was present).
CVE-2023-52614 2 Linux, Redhat 2 Linux Kernel, Enterprise Linux 2024-12-19 7.8 High
In the Linux kernel, the following vulnerability has been resolved: PM / devfreq: Fix buffer overflow in trans_stat_show Fix buffer overflow in trans_stat_show(). Convert simple snprintf to the more secure scnprintf with size of PAGE_SIZE. Add condition checking if we are exceeding PAGE_SIZE and exit early from loop. Also add at the end a warning that we exceeded PAGE_SIZE and that stats is disabled. Return -EFBIG in the case where we don't have enough space to write the full transition table. Also document in the ABI that this function can return -EFBIG error.
CVE-2023-52612 2024-12-19 6.0 Medium
In the Linux kernel, the following vulnerability has been resolved: crypto: scomp - fix req->dst buffer overflow The req->dst buffer size should be checked before copying from the scomp_scratch->dst to avoid req->dst buffer overflow problem.
CVE-2023-52606 1 Redhat 1 Enterprise Linux 2024-12-19 7.1 High
In the Linux kernel, the following vulnerability has been resolved: powerpc/lib: Validate size for vector operations Some of the fp/vmx code in sstep.c assume a certain maximum size for the instructions being emulated. The size of those operations however is determined separately in analyse_instr(). Add a check to validate the assumption on the maximum size of the operations, so as to prevent any unintended kernel stack corruption.
CVE-2023-52519 2024-12-19 6.0 Medium
In the Linux kernel, the following vulnerability has been resolved: HID: intel-ish-hid: ipc: Disable and reenable ACPI GPE bit The EHL (Elkhart Lake) based platforms provide a OOB (Out of band) service, which allows to wakup device when the system is in S5 (Soft-Off state). This OOB service can be enabled/disabled from BIOS settings. When enabled, the ISH device gets PME wake capability. To enable PME wakeup, driver also needs to enable ACPI GPE bit. On resume, BIOS will clear the wakeup bit. So driver need to re-enable it in resume function to keep the next wakeup capability. But this BIOS clearing of wakeup bit doesn't decrement internal OS GPE reference count, so this reenabling on every resume will cause reference count to overflow. So first disable and reenable ACPI GPE bit using acpi_disable_gpe().
CVE-2022-48711 2024-12-19 5.3 Medium
In the Linux kernel, the following vulnerability has been resolved: tipc: improve size validations for received domain records The function tipc_mon_rcv() allows a node to receive and process domain_record structs from peer nodes to track their views of the network topology. This patch verifies that the number of members in a received domain record does not exceed the limit defined by MAX_MON_DOMAIN, something that may otherwise lead to a stack overflow. tipc_mon_rcv() is called from the function tipc_link_proto_rcv(), where we are reading a 32 bit message data length field into a uint16. To avert any risk of bit overflow, we add an extra sanity check for this in that function. We cannot see that happen with the current code, but future designers being unaware of this risk, may introduce it by allowing delivery of very large (> 64k) sk buffers from the bearer layer. This potential problem was identified by Eric Dumazet. This fixes CVE-2022-0435
CVE-2021-47567 2024-12-19 5.5 Medium
In the Linux kernel, the following vulnerability has been resolved: powerpc/32: Fix hardlockup on vmap stack overflow Since the commit c118c7303ad5 ("powerpc/32: Fix vmap stack - Do not activate MMU before reading task struct") a vmap stack overflow results in a hard lockup. This is because emergency_ctx is still addressed with its virtual address allthough data MMU is not active anymore at that time. Fix it by using a physical address instead.
CVE-2021-47465 2024-12-19 7.1 High
In the Linux kernel, the following vulnerability has been resolved: KVM: PPC: Book3S HV: Fix stack handling in idle_kvm_start_guest() In commit 10d91611f426 ("powerpc/64s: Reimplement book3s idle code in C") kvm_start_guest() became idle_kvm_start_guest(). The old code allocated a stack frame on the emergency stack, but didn't use the frame to store anything, and also didn't store anything in its caller's frame. idle_kvm_start_guest() on the other hand is written more like a normal C function, it creates a frame on entry, and also stores CR/LR into its callers frame (per the ABI). The problem is that there is no caller frame on the emergency stack. The emergency stack for a given CPU is allocated with: paca_ptrs[i]->emergency_sp = alloc_stack(limit, i) + THREAD_SIZE; So emergency_sp actually points to the first address above the emergency stack allocation for a given CPU, we must not store above it without first decrementing it to create a frame. This is different to the regular kernel stack, paca->kstack, which is initialised to point at an initial frame that is ready to use. idle_kvm_start_guest() stores the backchain, CR and LR all of which write outside the allocation for the emergency stack. It then creates a stack frame and saves the non-volatile registers. Unfortunately the frame it creates is not large enough to fit the non-volatiles, and so the saving of the non-volatile registers also writes outside the emergency stack allocation. The end result is that we corrupt whatever is at 0-24 bytes, and 112-248 bytes above the emergency stack allocation. In practice this has gone unnoticed because the memory immediately above the emergency stack happens to be used for other stack allocations, either another CPUs mc_emergency_sp or an IRQ stack. See the order of calls to irqstack_early_init() and emergency_stack_init(). The low addresses of another stack are the top of that stack, and so are only used if that stack is under extreme pressue, which essentially never happens in practice - and if it did there's a high likelyhood we'd crash due to that stack overflowing. Still, we shouldn't be corrupting someone else's stack, and it is purely luck that we aren't corrupting something else. To fix it we save CR/LR into the caller's frame using the existing r1 on entry, we then create a SWITCH_FRAME_SIZE frame (which has space for pt_regs) on the emergency stack with the backchain pointing to the existing stack, and then finally we switch to the new frame on the emergency stack.