bpf: Make the verifier recognize llvm register allocation patterns. #190
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The llvm register allocator may use two different registers representing the same virtual register. In such case the following pattern can be observed: 1047: (bf) r9 = r6 1048: (a5) if r6 < 0x1000 goto pc+1 1050: ... 1051: (a5) if r9 < 0x2 goto pc+66 1052: ... 1053: (bf) r2 = r9 /* r2 needs to have upper and lower bounds */ In order to track this information without backtracking allocate ID for scalars in a similar way as it's done for find_good_pkt_pointers(). When the verifier encounters r9 = r6 assignment it will assign the same ID to both registers. Later if either register range is narrowed via conditional jump propagate the register state into the other register. Clear register ID in adjust_reg_min_max_vals() for any alu instruction. Newly allocated register ID is ignored for scalars in regsafe() and doesn't affect state pruning. mark_reg_unknown() also clears the ID. Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Under register pressure the llvm may spill registers with bounds into the stack. The verifier has to track them through spill/fill otherwise many kinds of bound errors will be seen. The spill/fill of induction variables was already happening. This patch extends this logic from tracking spill/fill of a constant into any bounded register. There is no need to track spill/fill of unbounded, since no new information will be retrieved from the stack during register fill. Though extra stack difference could cause state pruning to be less effective, no adverse affects were seen from this patch on selftests and on cilium programs. Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The main purpose of the profiler test to check different llvm generation patterns to make sure the verifier can load these large programs. Note that profiler.inc.h test doesn't follow strict kernel coding style. The code was formatted in kernel style, but variable declarations are kept as-is to preserve original llvm IR pattern. Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Master branch: 67ed375 |
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Ilya Leoshkevich says: ==================== v2: https://lore.kernel.org/bpf/20230128000650.1516334-1-iii@linux.ibm.com/#t v2 -> v3: - Make __arch_prepare_bpf_trampoline static. (Reported-by: kernel test robot <lkp@intel.com>) - Support both old- and new- style map definitions in sk_assign. (Alexei) - Trim DENYLIST.s390x. (Alexei) - Adjust s390x vmlinux path in vmtest.sh. - Drop merged fixes. v1: https://lore.kernel.org/bpf/20230125213817.1424447-1-iii@linux.ibm.com/#t v1 -> v2: - Fix core_read_macros, sk_assign, test_profiler, test_bpffs (24/31; I'm not quite happy with the fix, but don't have better ideas), and xdp_synproxy. (Andrii) - Prettify liburandom_read and verify_pkcs7_sig fixes. (Andrii) - Fix bpf_usdt_arg using barrier_var(); prettify barrier_var(). (Andrii) - Change BPF_MAX_TRAMP_LINKS to enum and query it using BTF. (Andrii) - Improve bpf_jit_supports_kfunc_call() description. (Alexei) - Always check sign_extend() return value. - Cc: Alexander Gordeev. Hi, This series implements poke, trampoline, kfunc, and mixing subprogs and tailcalls on s390x. The following failures still remain: #82 get_stack_raw_tp:FAIL get_stack_print_output:FAIL:user_stack corrupted user stack Known issue: We cannot reliably unwind userspace on s390x without DWARF. #101 ksyms_module:FAIL address of kernel function bpf_testmod_test_mod_kfunc is out of range Known issue: Kernel and modules are too far away from each other on s390x. #190 stacktrace_build_id:FAIL Known issue: We cannot reliably unwind userspace on s390x without DWARF. #281 xdp_metadata:FAIL See patch 6. None of these seem to be due to the new changes. Best regards, Ilya ==================== Signed-off-by: Alexei Starovoitov <ast@kernel.org>
kernel-patches-daemon-bpf bot
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We got a NULL pointer dereference issue below while running generic/475 I/O failure pressure test. BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] PREEMPT SMP PTI CPU: 1 PID: 15600 Comm: fsstress Not tainted 6.4.0-rc5-xfstests-00055-gd3ab1bca26b4 #190 RIP: 0010:jbd2_journal_set_features+0x13d/0x430 ... Call Trace: <TASK> ? __die+0x23/0x60 ? page_fault_oops+0xa4/0x170 ? exc_page_fault+0x67/0x170 ? asm_exc_page_fault+0x26/0x30 ? jbd2_journal_set_features+0x13d/0x430 jbd2_journal_revoke+0x47/0x1e0 __ext4_forget+0xc3/0x1b0 ext4_free_blocks+0x214/0x2f0 ext4_free_branches+0xeb/0x270 ext4_ind_truncate+0x2bf/0x320 ext4_truncate+0x1e4/0x490 ext4_handle_inode_extension+0x1bd/0x2a0 ? iomap_dio_complete+0xaf/0x1d0 The root cause is the journal super block had been failed to write out due to I/O fault injection, it's uptodate bit was cleared by end_buffer_write_sync() and didn't reset yet in jbd2_write_superblock(). And it raced by journal_get_superblock()->bh_read(), unfortunately, the read IO is also failed, so the error handling in journal_fail_superblock() unexpectedly clear the journal->j_sb_buffer, finally lead to above NULL pointer dereference issue. If the journal super block had been read and verified, there is no need to call bh_read() read it again even if it has been failed to written out. So the fix could be simply move buffer_verified(bh) in front of bh_read(). Also remove a stale comment left in jbd2_journal_check_used_features(). Fixes: 51bacdba23d8 ("jbd2: factor out journal initialization from journal_get_superblock()") Reported-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Zhang Yi <yi.zhang@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20230616015547.3155195-1-yi.zhang@huaweicloud.com Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Pull request for series with
subject: bpf: Make the verifier recognize llvm register allocation patterns.
version: 1
url: https://patchwork.kernel.org/project/bpf/list/?series=360473