CVE-2022-49658

bpf: Fix insufficient bounds propagation from adjust_scalar_min_max_vals

Published Feb 26, 2025 CVSS 3.1 · 5.5 Medium EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix insufficient bounds propagation from adjust_scalar_min_max_vals

Kuee reported a corner case where the tnum becomes constant after the call
to __reg_bound_offset(), but the register's bounds are not, that is, its
min bounds are still not equal to the register's max bounds.

This in turn allows to leak pointers through turning a pointer register as
is into an unknown scalar via adjust_ptr_min_max_vals().

Before:

func#0 @0
0: R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0))
0: (b7) r0 = 1 ; R0_w=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0))
1: (b7) r3 = 0 ; R3_w=scalar(imm=0,umax=0,var_off=(0x0; 0x0))
2: (87) r3 = -r3 ; R3_w=scalar()
3: (87) r3 = -r3 ; R3_w=scalar()
4: (47) r3 |= 32767 ; R3_w=scalar(smin=-9223372036854743041,umin=32767,var_off=(0x7fff; 0xffffffffffff8000),s32_min=-2147450881)
5: (75) if r3 s>= 0x0 goto pc+1 ; R3_w=scalar(umin=9223372036854808575,var_off=(0x8000000000007fff; 0x7fffffffffff8000),s32_min=-2147450881,u32_min=32767)
6: (95) exit

from 5 to 7: R0=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R3=scalar(umin=32767,umax=9223372036854775807,var_off=(0x7fff; 0x7fffffffffff8000),s32_min=-2147450881) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0))
7: (d5) if r3 s<= 0x8000 goto pc+1 ; R3=scalar(umin=32769,umax=9223372036854775807,var_off=(0x7fff; 0x7fffffffffff8000),s32_min=-2147450881,u32_min=32767)
8: (95) exit

from 7 to 9: R0=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R3=scalar(umin=32767,umax=32768,var_off=(0x7fff; 0x8000)) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0))
9: (07) r3 += -32767 ; R3_w=scalar(imm=0,umax=1,var_off=(0x0; 0x0)) <--- [*]
10: (95) exit

What can be seen here is that R3=scalar(umin=32767,umax=32768,var_off=(0x7fff;
0x8000)) after the operation R3 += -32767 results in a 'malformed' constant, that
is, R3_w=scalar(imm=0,umax=1,var_off=(0x0; 0x0)). Intersecting with var_off has
not been done at that point via __update_reg_bounds(), which would have improved
the umax to be equal to umin.

Refactor the tnum <> min/max bounds information flow into a reg_bounds_sync()
helper and use it consistently everywhere. After the fix, bounds have been
corrected to R3_w=scalar(imm=0,umax=0,var_off=(0x0; 0x0)) and thus the register
is regarded as a 'proper' constant scalar of 0.

After:

func#0 @0
0: R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0))
0: (b7) r0 = 1 ; R0_w=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0))
1: (b7) r3 = 0 ; R3_w=scalar(imm=0,umax=0,var_off=(0x0; 0x0))
2: (87) r3 = -r3 ; R3_w=scalar()
3: (87) r3 = -r3 ; R3_w=scalar()
4: (47) r3 |= 32767 ; R3_w=scalar(smin=-9223372036854743041,umin=32767,var_off=(0x7fff; 0xffffffffffff8000),s32_min=-2147450881)
5: (75) if r3 s>= 0x0 goto pc+1 ; R3_w=scalar(umin=9223372036854808575,var_off=(0x8000000000007fff; 0x7fffffffffff8000),s32_min=-2147450881,u32_min=32767)
6: (95) exit

from 5 to 7: R0=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R3=scalar(umin=32767,umax=9223372036854775807,var_off=(0x7fff; 0x7fffffffffff8000),s32_min=-2147450881) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0))
7: (d5) if r3 s<= 0x8000 goto pc+1 ; R3=scalar(umin=32769,umax=9223372036854775807,var_off=(0x7fff; 0x7fffffffffff8000),s32_min=-2147450881,u32_min=32767)
8: (95) exit

from 7 to 9: R0=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R3=scalar(umin=32767,umax=32768,var_off=(0x7fff; 0x8000)) R10=fp(off=0
---truncated---

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
EUVD EUVD EUVD-2022-54574 In the Linux kernel, the following vulnerability has been resolved: bpf: Fix insufficient bounds propagation from adjust_scalar_min_max_vals Kuee reported a corner case where the tnum becomes constant after the call to __reg_bound_offset(), but the register's bounds are not, that is, its min bounds are still not equal to the register's max bounds. This in turn allows to leak pointers through turning a pointer register as is into an unknown scalar via adjust_ptr_min_max_vals(). Before: func#0 @0 0: R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) 0: (b7) r0 = 1 ; R0_w=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) 1: (b7) r3 = 0 ; R3_w=scalar(imm=0,umax=0,var_off=(0x0; 0x0)) 2: (87) r3 = -r3 ; R3_w=scalar() 3: (87) r3 = -r3 ; R3_w=scalar() 4: (47) r3 |= 32767 ; R3_w=scalar(smin=-9223372036854743041,umin=32767,var_off=(0x7fff; 0xffffffffffff8000),s32_min=-2147450881) 5: (75) if r3 s>= 0x0 goto pc+1 ; R3_w=scalar(umin=9223372036854808575,var_off=(0x8000000000007fff; 0x7fffffffffff8000),s32_min=-2147450881,u32_min=32767) 6: (95) exit from 5 to 7: R0=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R3=scalar(umin=32767,umax=9223372036854775807,var_off=(0x7fff; 0x7fffffffffff8000),s32_min=-2147450881) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) 7: (d5) if r3 s<= 0x8000 goto pc+1 ; R3=scalar(umin=32769,umax=9223372036854775807,var_off=(0x7fff; 0x7fffffffffff8000),s32_min=-2147450881,u32_min=32767) 8: (95) exit from 7 to 9: R0=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R3=scalar(umin=32767,umax=32768,var_off=(0x7fff; 0x8000)) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) 9: (07) r3 += -32767 ; R3_w=scalar(imm=0,umax=1,var_off=(0x0; 0x0)) <--- [*] 10: (95) exit What can be seen here is that R3=scalar(umin=32767,umax=32768,var_off=(0x7fff; 0x8000)) after the operation R3 += -32767 results in a 'malformed' constant, that is, R3_w=scalar(imm=0,umax=1,var_off=(0x0; 0x0)). Intersecting with var_off has not been done at that point via __update_reg_bounds(), which would have improved the umax to be equal to umin. Refactor the tnum <> min/max bounds information flow into a reg_bounds_sync() helper and use it consistently everywhere. After the fix, bounds have been corrected to R3_w=scalar(imm=0,umax=0,var_off=(0x0; 0x0)) and thus the register is regarded as a 'proper' constant scalar of 0. After: func#0 @0 0: R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) 0: (b7) r0 = 1 ; R0_w=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) 1: (b7) r3 = 0 ; R3_w=scalar(imm=0,umax=0,var_off=(0x0; 0x0)) 2: (87) r3 = -r3 ; R3_w=scalar() 3: (87) r3 = -r3 ; R3_w=scalar() 4: (47) r3 |= 32767 ; R3_w=scalar(smin=-9223372036854743041,umin=32767,var_off=(0x7fff; 0xffffffffffff8000),s32_min=-2147450881) 5: (75) if r3 s>= 0x0 goto pc+1 ; R3_w=scalar(umin=9223372036854808575,var_off=(0x8000000000007fff; 0x7fffffffffff8000),s32_min=-2147450881,u32_min=32767) 6: (95) exit from 5 to 7: R0=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R3=scalar(umin=32767,umax=9223372036854775807,var_off=(0x7fff; 0x7fffffffffff8000),s32_min=-2147450881) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) 7: (d5) if r3 s<= 0x8000 goto pc+1 ; R3=scalar(umin=32769,umax=9223372036854775807,var_off=(0x7fff; 0x7fffffffffff8000),s32_min=-2147450881,u32_min=32767) 8: (95) exit from 7 to 9: R0=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R3=scalar(umin=32767,umax=32768,var_off=(0x7fff; 0x8000)) R10=fp(off=0 ---truncated---
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Linux linux Kernel
Weaknesses NVD-CWE-noinfo
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.19:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.19:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.19:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.19:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:5.19:rc5:*:*:*:*:*:*
Vendors & Products Linux linux Kernel
Metrics cvssV3_1

{'score': 6.0, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:H'}

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

Type Values Removed Values Added
Weaknesses CWE-401
Metrics cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

cvssV3_1

{'score': 6.0, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:H'}

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: bpf: Fix insufficient bounds propagation from adjust_scalar_min_max_vals Kuee reported a corner case where the tnum becomes constant after the call to __reg_bound_offset(), but the register's bounds are not, that is, its min bounds are still not equal to the register's max bounds. This in turn allows to leak pointers through turning a pointer register as is into an unknown scalar via adjust_ptr_min_max_vals(). Before: func#0 @0 0: R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) 0: (b7) r0 = 1 ; R0_w=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) 1: (b7) r3 = 0 ; R3_w=scalar(imm=0,umax=0,var_off=(0x0; 0x0)) 2: (87) r3 = -r3 ; R3_w=scalar() 3: (87) r3 = -r3 ; R3_w=scalar() 4: (47) r3 |= 32767 ; R3_w=scalar(smin=-9223372036854743041,umin=32767,var_off=(0x7fff; 0xffffffffffff8000),s32_min=-2147450881) 5: (75) if r3 s>= 0x0 goto pc+1 ; R3_w=scalar(umin=9223372036854808575,var_off=(0x8000000000007fff; 0x7fffffffffff8000),s32_min=-2147450881,u32_min=32767) 6: (95) exit from 5 to 7: R0=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R3=scalar(umin=32767,umax=9223372036854775807,var_off=(0x7fff; 0x7fffffffffff8000),s32_min=-2147450881) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) 7: (d5) if r3 s<= 0x8000 goto pc+1 ; R3=scalar(umin=32769,umax=9223372036854775807,var_off=(0x7fff; 0x7fffffffffff8000),s32_min=-2147450881,u32_min=32767) 8: (95) exit from 7 to 9: R0=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R3=scalar(umin=32767,umax=32768,var_off=(0x7fff; 0x8000)) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) 9: (07) r3 += -32767 ; R3_w=scalar(imm=0,umax=1,var_off=(0x0; 0x0)) <--- [*] 10: (95) exit What can be seen here is that R3=scalar(umin=32767,umax=32768,var_off=(0x7fff; 0x8000)) after the operation R3 += -32767 results in a 'malformed' constant, that is, R3_w=scalar(imm=0,umax=1,var_off=(0x0; 0x0)). Intersecting with var_off has not been done at that point via __update_reg_bounds(), which would have improved the umax to be equal to umin. Refactor the tnum <> min/max bounds information flow into a reg_bounds_sync() helper and use it consistently everywhere. After the fix, bounds have been corrected to R3_w=scalar(imm=0,umax=0,var_off=(0x0; 0x0)) and thus the register is regarded as a 'proper' constant scalar of 0. After: func#0 @0 0: R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) 0: (b7) r0 = 1 ; R0_w=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) 1: (b7) r3 = 0 ; R3_w=scalar(imm=0,umax=0,var_off=(0x0; 0x0)) 2: (87) r3 = -r3 ; R3_w=scalar() 3: (87) r3 = -r3 ; R3_w=scalar() 4: (47) r3 |= 32767 ; R3_w=scalar(smin=-9223372036854743041,umin=32767,var_off=(0x7fff; 0xffffffffffff8000),s32_min=-2147450881) 5: (75) if r3 s>= 0x0 goto pc+1 ; R3_w=scalar(umin=9223372036854808575,var_off=(0x8000000000007fff; 0x7fffffffffff8000),s32_min=-2147450881,u32_min=32767) 6: (95) exit from 5 to 7: R0=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R3=scalar(umin=32767,umax=9223372036854775807,var_off=(0x7fff; 0x7fffffffffff8000),s32_min=-2147450881) R10=fp(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) 7: (d5) if r3 s<= 0x8000 goto pc+1 ; R3=scalar(umin=32769,umax=9223372036854775807,var_off=(0x7fff; 0x7fffffffffff8000),s32_min=-2147450881,u32_min=32767) 8: (95) exit from 7 to 9: R0=scalar(imm=1,umin=1,umax=1,var_off=(0x1; 0x0)) R1=ctx(off=0,imm=0,umax=0,var_off=(0x0; 0x0)) R3=scalar(umin=32767,umax=32768,var_off=(0x7fff; 0x8000)) R10=fp(off=0 ---truncated---
Title bpf: Fix insufficient bounds propagation from adjust_scalar_min_max_vals
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Nov 5, 2026, 7:49 PM
Reserved
Feb 26, 2025, 2:21 AM
Status
Analyzed
Published
Feb 26, 2025, 7:01 AM
Modified
Nov 5, 2026, 8:17 PM
Severity
Moderate
Public date
Feb 26, 2025, 12:00 AM