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authorDaniel Borkmann <daniel@iogearbox.net>2021-04-23 16:59:55 +0300
committerDaniel Borkmann <daniel@iogearbox.net>2021-04-27 18:13:49 +0300
commit10bf4e83167cc68595b85fd73bb91e8f2c086e36 (patch)
treee07a78d2e184b152b8cbd85c2928002554ccc33f /kernel/bpf
parent38d26d89b31d0766d431471572cc9b007ca19c98 (diff)
downloadlinux-10bf4e83167cc68595b85fd73bb91e8f2c086e36.tar.xz
bpf: Fix propagation of 32 bit unsigned bounds from 64 bit bounds
Similarly as b02709587ea3 ("bpf: Fix propagation of 32-bit signed bounds from 64-bit bounds."), we also need to fix the propagation of 32 bit unsigned bounds from 64 bit counterparts. That is, really only set the u32_{min,max}_value when /both/ {umin,umax}_value safely fit in 32 bit space. For example, the register with a umin_value == 1 does /not/ imply that u32_min_value is also equal to 1, since umax_value could be much larger than 32 bit subregister can hold, and thus u32_min_value is in the interval [0,1] instead. Before fix, invalid tracking result of R2_w=inv1: [...] 5: R0_w=inv1337 R1=ctx(id=0,off=0,imm=0) R2_w=inv(id=0) R10=fp0 5: (35) if r2 >= 0x1 goto pc+1 [...] // goto path 7: R0=inv1337 R1=ctx(id=0,off=0,imm=0) R2=inv(id=0,umin_value=1) R10=fp0 7: (b6) if w2 <= 0x1 goto pc+1 [...] // goto path 9: R0=inv1337 R1=ctx(id=0,off=0,imm=0) R2=inv(id=0,smin_value=-9223372036854775807,smax_value=9223372032559808513,umin_value=1,umax_value=18446744069414584321,var_off=(0x1; 0xffffffff00000000),s32_min_value=1,s32_max_value=1,u32_max_value=1) R10=fp0 9: (bc) w2 = w2 10: R0=inv1337 R1=ctx(id=0,off=0,imm=0) R2_w=inv1 R10=fp0 [...] After fix, correct tracking result of R2_w=inv(id=0,umax_value=1,var_off=(0x0; 0x1)): [...] 5: R0_w=inv1337 R1=ctx(id=0,off=0,imm=0) R2_w=inv(id=0) R10=fp0 5: (35) if r2 >= 0x1 goto pc+1 [...] // goto path 7: R0=inv1337 R1=ctx(id=0,off=0,imm=0) R2=inv(id=0,umin_value=1) R10=fp0 7: (b6) if w2 <= 0x1 goto pc+1 [...] // goto path 9: R0=inv1337 R1=ctx(id=0,off=0,imm=0) R2=inv(id=0,smax_value=9223372032559808513,umax_value=18446744069414584321,var_off=(0x0; 0xffffffff00000001),s32_min_value=0,s32_max_value=1,u32_max_value=1) R10=fp0 9: (bc) w2 = w2 10: R0=inv1337 R1=ctx(id=0,off=0,imm=0) R2_w=inv(id=0,umax_value=1,var_off=(0x0; 0x1)) R10=fp0 [...] Thus, same issue as in b02709587ea3 holds for unsigned subregister tracking. Also, align __reg64_bound_u32() similarly to __reg64_bound_s32() as done in b02709587ea3 to make them uniform again. Fixes: 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking") Reported-by: Manfred Paul (@_manfp) Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: John Fastabend <john.fastabend@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/verifier.c8
1 files changed, 3 insertions, 5 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 637462e9b6ee..9145f88b2a0a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1398,9 +1398,7 @@ static bool __reg64_bound_s32(s64 a)
static bool __reg64_bound_u32(u64 a)
{
- if (a > U32_MIN && a < U32_MAX)
- return true;
- return false;
+ return a > U32_MIN && a < U32_MAX;
}
static void __reg_combine_64_into_32(struct bpf_reg_state *reg)
@@ -1411,10 +1409,10 @@ static void __reg_combine_64_into_32(struct bpf_reg_state *reg)
reg->s32_min_value = (s32)reg->smin_value;
reg->s32_max_value = (s32)reg->smax_value;
}
- if (__reg64_bound_u32(reg->umin_value))
+ if (__reg64_bound_u32(reg->umin_value) && __reg64_bound_u32(reg->umax_value)) {
reg->u32_min_value = (u32)reg->umin_value;
- if (__reg64_bound_u32(reg->umax_value))
reg->u32_max_value = (u32)reg->umax_value;
+ }
/* Intersecting with the old var_off might have improved our bounds
* slightly. e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),