From: Andrei Matei andreimatei1@gmail.com
mainline inclusion from mainline-v6.8-rc1 commit 1d38a9ee81570c4bd61f557832dead4d6f816760 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9Q9EW CVE: CVE-2023-52676
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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This patch promotes the arithmetic around checking stack bounds to be done in the 64-bit domain, instead of the current 32bit. The arithmetic implies adding together a 64-bit register with a int offset. The register was checked to be below 1<<29 when it was variable, but not when it was fixed. The offset either comes from an instruction (in which case it is 16 bit), from another register (in which case the caller checked it to be below 1<<29 [1]), or from the size of an argument to a kfunc (in which case it can be a u32 [2]). Between the register being inconsistently checked to be below 1<<29, and the offset being up to an u32, it appears that we were open to overflowing the `int`s which were currently used for arithmetic.
[1] https://github.com/torvalds/linux/blob/815fb87b753055df2d9e50f6cd80eb10235fe... [2] https://github.com/torvalds/linux/blob/815fb87b753055df2d9e50f6cd80eb10235fe...
Reported-by: Andrii Nakryiko andrii.nakryiko@gmail.com Signed-off-by: Andrei Matei andreimatei1@gmail.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Acked-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/20231207041150.229139-4-andreimatei1@gmail.com Conflicts: kernel/bpf/verifier.c [The conflict is because some modifications were merged by the commit db2a27bb5398e ("bpf: Fix accesses to uninit stack slots")] Signed-off-by: Pu Lehui pulehui@huawei.com --- kernel/bpf/verifier.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index d5706782be14..946e485a102c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3697,7 +3697,7 @@ static int check_stack_access_within_bounds( struct bpf_reg_state *regs = cur_regs(env); struct bpf_reg_state *reg = regs + regno; struct bpf_func_state *state = func(env, reg); - int min_off, max_off; + s64 min_off, max_off; int err; char *err_extra;
@@ -3710,7 +3710,7 @@ static int check_stack_access_within_bounds( err_extra = " write to";
if (tnum_is_const(reg->var_off)) { - min_off = reg->var_off.value + off; + min_off = (s64)reg->var_off.value + off; max_off = min_off + access_size; } else { if (reg->smax_value >= BPF_MAX_VAR_OFF ||