Unable to handle kernel paging request at virtual address 12005456 #134
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moved to openbmc/qemu repo openbmc/qemu#10 |
shenki
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Mar 20, 2020
commit ee63634 upstream. Dm-zoned initializes reference counters of new chunk works with zero value and refcount_inc() is called to increment the counter. However, the refcount_inc() function handles the addition to zero value as an error and triggers the warning as follows: refcount_t: addition on 0; use-after-free. WARNING: CPU: 7 PID: 1506 at lib/refcount.c:25 refcount_warn_saturate+0x68/0xf0 ... CPU: 7 PID: 1506 Comm: systemd-udevd Not tainted 5.4.0+ #134 ... Call Trace: dmz_map+0x2d2/0x350 [dm_zoned] __map_bio+0x42/0x1a0 __split_and_process_non_flush+0x14a/0x1b0 __split_and_process_bio+0x83/0x240 ? kmem_cache_alloc+0x165/0x220 dm_process_bio+0x90/0x230 ? generic_make_request_checks+0x2e7/0x680 dm_make_request+0x3e/0xb0 generic_make_request+0xcf/0x320 ? memcg_drain_all_list_lrus+0x1c0/0x1c0 submit_bio+0x3c/0x160 ? guard_bio_eod+0x2c/0x130 mpage_readpages+0x182/0x1d0 ? bdev_evict_inode+0xf0/0xf0 read_pages+0x6b/0x1b0 __do_page_cache_readahead+0x1ba/0x1d0 force_page_cache_readahead+0x93/0x100 generic_file_read_iter+0x83a/0xe40 ? __seccomp_filter+0x7b/0x670 new_sync_read+0x12a/0x1c0 vfs_read+0x9d/0x150 ksys_read+0x5f/0xe0 do_syscall_64+0x5b/0x180 entry_SYSCALL_64_after_hwframe+0x44/0xa9 ... After this warning, following refcount API calls for the counter all fail to change the counter value. Fix this by setting the initial reference counter value not zero but one for the new chunk works. Instead, do not call refcount_inc() via dmz_get_chunk_work() for the new chunks works. The failure was observed with linux version 5.4 with CONFIG_REFCOUNT_FULL enabled. Refcount rework was merged to linux version 5.5 by the commit 168829a ("Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip"). After this commit, CONFIG_REFCOUNT_FULL was removed and the failure was observed regardless of kernel configuration. Linux version 4.20 merged the commit 092b564 ("dm zoned: target: use refcount_t for dm zoned reference counters"). Before this commit, dm zoned used atomic_t APIs which does not check addition to zero, then this fix is not necessary. Fixes: 092b564 ("dm zoned: target: use refcount_t for dm zoned reference counters") Cc: stable@vger.kernel.org # 5.4+ Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com> Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
shenki
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May 24, 2021
[ Upstream commit 0f20615 ] Fix BPF_CORE_READ_BITFIELD() macro used for reading CO-RE-relocatable bitfields. Missing breaks in a switch caused 8-byte reads always. This can confuse libbpf because it does strict checks that memory load size corresponds to the original size of the field, which in this case quite often would be wrong. After fixing that, we run into another problem, which quite subtle, so worth documenting here. The issue is in Clang optimization and CO-RE relocation interactions. Without that asm volatile construct (also known as barrier_var()), Clang will re-order BYTE_OFFSET and BYTE_SIZE relocations and will apply BYTE_OFFSET 4 times for each switch case arm. This will result in the same error from libbpf about mismatch of memory load size and original field size. I.e., if we were reading u32, we'd still have *(u8 *), *(u16 *), *(u32 *), and *(u64 *) memory loads, three of which will fail. Using barrier_var() forces Clang to apply BYTE_OFFSET relocation first (and once) to calculate p, after which value of p is used without relocation in each of switch case arms, doing appropiately-sized memory load. Here's the list of relevant relocations and pieces of generated BPF code before and after this patch for test_core_reloc_bitfields_direct selftests. BEFORE ===== #45: core_reloc: insn #160 --> [5] + 0:5: byte_sz --> struct core_reloc_bitfields.u32 #46: core_reloc: insn #167 --> [5] + 0:5: byte_off --> struct core_reloc_bitfields.u32 #47: core_reloc: insn #174 --> [5] + 0:5: byte_off --> struct core_reloc_bitfields.u32 #48: core_reloc: insn #178 --> [5] + 0:5: byte_off --> struct core_reloc_bitfields.u32 #49: core_reloc: insn #182 --> [5] + 0:5: byte_off --> struct core_reloc_bitfields.u32 157: 18 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 r2 = 0 ll 159: 7b 12 20 01 00 00 00 00 *(u64 *)(r2 + 288) = r1 160: b7 02 00 00 04 00 00 00 r2 = 4 ; BYTE_SIZE relocation here ^^^ 161: 66 02 07 00 03 00 00 00 if w2 s> 3 goto +7 <LBB0_63> 162: 16 02 0d 00 01 00 00 00 if w2 == 1 goto +13 <LBB0_65> 163: 16 02 01 00 02 00 00 00 if w2 == 2 goto +1 <LBB0_66> 164: 05 00 12 00 00 00 00 00 goto +18 <LBB0_69> 0000000000000528 <LBB0_66>: 165: 18 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 r1 = 0 ll 167: 69 11 08 00 00 00 00 00 r1 = *(u16 *)(r1 + 8) ; BYTE_OFFSET relo here w/ WRONG size ^^^^^^^^^^^^^^^^ 168: 05 00 0e 00 00 00 00 00 goto +14 <LBB0_69> 0000000000000548 <LBB0_63>: 169: 16 02 0a 00 04 00 00 00 if w2 == 4 goto +10 <LBB0_67> 170: 16 02 01 00 08 00 00 00 if w2 == 8 goto +1 <LBB0_68> 171: 05 00 0b 00 00 00 00 00 goto +11 <LBB0_69> 0000000000000560 <LBB0_68>: 172: 18 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 r1 = 0 ll 174: 79 11 08 00 00 00 00 00 r1 = *(u64 *)(r1 + 8) ; BYTE_OFFSET relo here w/ WRONG size ^^^^^^^^^^^^^^^^ 175: 05 00 07 00 00 00 00 00 goto +7 <LBB0_69> 0000000000000580 <LBB0_65>: 176: 18 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 r1 = 0 ll 178: 71 11 08 00 00 00 00 00 r1 = *(u8 *)(r1 + 8) ; BYTE_OFFSET relo here w/ WRONG size ^^^^^^^^^^^^^^^^ 179: 05 00 03 00 00 00 00 00 goto +3 <LBB0_69> 00000000000005a0 <LBB0_67>: 180: 18 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 r1 = 0 ll 182: 61 11 08 00 00 00 00 00 r1 = *(u32 *)(r1 + 8) ; BYTE_OFFSET relo here w/ RIGHT size ^^^^^^^^^^^^^^^^ 00000000000005b8 <LBB0_69>: 183: 67 01 00 00 20 00 00 00 r1 <<= 32 184: b7 02 00 00 00 00 00 00 r2 = 0 185: 16 02 02 00 00 00 00 00 if w2 == 0 goto +2 <LBB0_71> 186: c7 01 00 00 20 00 00 00 r1 s>>= 32 187: 05 00 01 00 00 00 00 00 goto +1 <LBB0_72> 00000000000005e0 <LBB0_71>: 188: 77 01 00 00 20 00 00 00 r1 >>= 32 AFTER ===== #30: core_reloc: insn #132 --> [5] + 0:5: byte_off --> struct core_reloc_bitfields.u32 #31: core_reloc: insn #134 --> [5] + 0:5: byte_sz --> struct core_reloc_bitfields.u32 129: 18 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 r2 = 0 ll 131: 7b 12 20 01 00 00 00 00 *(u64 *)(r2 + 288) = r1 132: b7 01 00 00 08 00 00 00 r1 = 8 ; BYTE_OFFSET relo here ^^^ ; no size check for non-memory dereferencing instructions 133: 0f 12 00 00 00 00 00 00 r2 += r1 134: b7 03 00 00 04 00 00 00 r3 = 4 ; BYTE_SIZE relocation here ^^^ 135: 66 03 05 00 03 00 00 00 if w3 s> 3 goto +5 <LBB0_63> 136: 16 03 09 00 01 00 00 00 if w3 == 1 goto +9 <LBB0_65> 137: 16 03 01 00 02 00 00 00 if w3 == 2 goto +1 <LBB0_66> 138: 05 00 0a 00 00 00 00 00 goto +10 <LBB0_69> 0000000000000458 <LBB0_66>: 139: 69 21 00 00 00 00 00 00 r1 = *(u16 *)(r2 + 0) ; NO CO-RE relocation here ^^^^^^^^^^^^^^^^ 140: 05 00 08 00 00 00 00 00 goto +8 <LBB0_69> 0000000000000468 <LBB0_63>: 141: 16 03 06 00 04 00 00 00 if w3 == 4 goto +6 <LBB0_67> 142: 16 03 01 00 08 00 00 00 if w3 == 8 goto +1 <LBB0_68> 143: 05 00 05 00 00 00 00 00 goto +5 <LBB0_69> 0000000000000480 <LBB0_68>: 144: 79 21 00 00 00 00 00 00 r1 = *(u64 *)(r2 + 0) ; NO CO-RE relocation here ^^^^^^^^^^^^^^^^ 145: 05 00 03 00 00 00 00 00 goto +3 <LBB0_69> 0000000000000490 <LBB0_65>: 146: 71 21 00 00 00 00 00 00 r1 = *(u8 *)(r2 + 0) ; NO CO-RE relocation here ^^^^^^^^^^^^^^^^ 147: 05 00 01 00 00 00 00 00 goto +1 <LBB0_69> 00000000000004a0 <LBB0_67>: 148: 61 21 00 00 00 00 00 00 r1 = *(u32 *)(r2 + 0) ; NO CO-RE relocation here ^^^^^^^^^^^^^^^^ 00000000000004a8 <LBB0_69>: 149: 67 01 00 00 20 00 00 00 r1 <<= 32 150: b7 02 00 00 00 00 00 00 r2 = 0 151: 16 02 02 00 00 00 00 00 if w2 == 0 goto +2 <LBB0_71> 152: c7 01 00 00 20 00 00 00 r1 s>>= 32 153: 05 00 01 00 00 00 00 00 goto +1 <LBB0_72> 00000000000004d0 <LBB0_71>: 154: 77 01 00 00 20 00 00 00 r1 >>= 323 Fixes: ee26dad ("libbpf: Add support for relocatable bitfields") Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Lorenz Bauer <lmb@cloudflare.com> Link: https://lore.kernel.org/bpf/20210426192949.416837-4-andrii@kernel.org Signed-off-by: Sasha Levin <sashal@kernel.org>
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Encountered the following oops running under qemu v2.9.0-189-gb4b9a30f8ce1-dirty
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