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CVE PROGRAM SOURCE RECORDUnscored

CVE-2026-97921

tracing: Free histogram the field rejected for a bad modifier

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: tracing: Free histogram the field rejected for a bad modifier Writing a hist trigger whose value or variable carries a modifier that is not allowed there leaks the fields that were built for it. __create_val_field() takes the field from parse_expr() and stores it in hist_data->fields[] only after the modifier checks have run: hist_field = parse_expr(hist_data, file, field_str, flags, var_name, &n_subexprs); ... if (hist_field->flags & HIST_FIELD_FL_VAR) { if (hist_field->flags & (...)) goto err; } else { if (hist_field->flags & (...)) goto err; } hist_data->fields[val_idx] = hist_field; Both checks jump past that store, and the err label returns without freeing anything. The error unwinds to create_hist_data(), which calls destroy_hist_data() -> destroy_hist_fields(), and that reaches a field only by walking fields[]. A field that never got there is unreachable. commit e0213434fe3e ("tracing: Do not let histogram values have some modifiers") set ret to -EINVAL and fell through to the store, which left the field owned by fields[] and freed along with the rest of hist_data. Splitting the check into a value case and a variable case replaced that fall-through with a goto that skips it. With CONFIG_DEBUG_KMEMLEAK, 200 writes of # echo 'hist:keys=prev_pid:vals=next_pid.log2' > \ events/sched/sched_switch/trigger each correctly rejected with -EINVAL, leave 332 unreferenced objects (63744 bytes) reported at create_hist_field(); 200 install and remove cycles of a valid trigger leave none. A '.log2' field is two allocations, since create_hist_field() puts the plain field in operands[0] of the log2 field, and both are reported. Use destroy_hist_field() rather than __destroy_hist_field() so that operands[0] is freed as well. It returns early for HIST_FIELD_FL_VAR_REF, which is what an operand owned by hist_data->var_refs[] needs; the rejected field itself is never a var ref, because a var ref never carries a modifier flag.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 7403630eb94c1d664fb873f967427ef2f6ee3699 to < a2652fcf96b63e9da04951e4e58e6a0672df695daffected
  • e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c to < 3d42fed18b2c5707b6332ebe87b789fd768eb01baffected
  • e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c to < e787361bb6b0026ea3eb4d3fa7a304c7fcb99555affected
  • e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c to < b22dc0add7d72b8bd9cae3188db0dd65da1c8652affected
  • e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c to < 891c21f6d5673b2a519b536243bfc6dd2d35beb6affected
  • e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c to < 230234d12ce42ab04132a32c3a848f07a5d27a71affected
  • 8d505d06d7330f5d67d3e5e9e1c647fb0b10ddadaffected
  • 6.1.33 to < 6.1.189affected
  • 6.3.7 to < 6.4affected

Linux Linux

Default version status: affected

  • 6.4affected
  • 0 to < 6.4unaffected
  • 6.1.189 to ≤ 6.1.*unaffected
  • 6.6.158 to ≤ 6.6.*unaffected
  • 6.12.111 to ≤ 6.12.*unaffected
  • 6.18.53 to ≤ 6.18.*unaffected
  • 7.2.7 to ≤ 7.2.*unaffected
  • 7.3 to ≤ *unaffected

References