{"id":"CVE-2026-97921","state":"PUBLISHED","title":"tracing: Free histogram the field rejected for a bad modifier","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Free histogram the field rejected for a bad modifier\n\nWriting a hist trigger whose value or variable carries a modifier that is\nnot allowed there leaks the fields that were built for it.\n\n__create_val_field() takes the field from parse_expr() and stores it in\nhist_data->fields[] only after the modifier checks have run:\n\n\thist_field = parse_expr(hist_data, file, field_str, flags, var_name,\n\t\t\t\t&n_subexprs);\n\t...\n\tif (hist_field->flags & HIST_FIELD_FL_VAR) {\n\t\tif (hist_field->flags & (...))\n\t\t\tgoto err;\n\t} else {\n\t\tif (hist_field->flags & (...))\n\t\t\tgoto err;\n\t}\n\n\thist_data->fields[val_idx] = hist_field;\n\nBoth checks jump past that store, and the err label returns without\nfreeing anything. The error unwinds to create_hist_data(), which calls\ndestroy_hist_data() -> destroy_hist_fields(), and that reaches a field\nonly by walking fields[]. A field that never got there is unreachable.\n\ncommit e0213434fe3e (\"tracing: Do not let histogram values have some\nmodifiers\") set ret to -EINVAL and fell through to the store, which left\nthe field owned by fields[] and freed along with the rest of hist_data.\nSplitting the check into a value case and a variable case replaced that\nfall-through with a goto that skips it.\n\nWith CONFIG_DEBUG_KMEMLEAK, 200 writes of\n\n  # echo 'hist:keys=prev_pid:vals=next_pid.log2' > \\\n\t events/sched/sched_switch/trigger\n\neach correctly rejected with -EINVAL, leave 332 unreferenced objects\n(63744 bytes) reported at create_hist_field(); 200 install and remove\ncycles of a valid trigger leave none. A '.log2' field is two\nallocations, since create_hist_field() puts the plain field in\noperands[0] of the log2 field, and both are reported.\n\nUse destroy_hist_field() rather than __destroy_hist_field() so that\noperands[0] is freed as well. It returns early for HIST_FIELD_FL_VAR_REF,\nwhich is what an operand owned by hist_data->var_refs[] needs; the\nrejected field itself is never a var ref, because a var ref never carries\na modifier flag.","publishedAt":"2026-09-25T10:22:41.081Z","updatedAt":"2026-10-19T09:10:48.148Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"7403630eb94c1d664fb873f967427ef2f6ee3699","status":"affected","lessThan":"a2652fcf96b63e9da04951e4e58e6a0672df695d","versionType":"git"},{"version":"e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c","status":"affected","lessThan":"3d42fed18b2c5707b6332ebe87b789fd768eb01b","versionType":"git"},{"version":"e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c","status":"affected","lessThan":"e787361bb6b0026ea3eb4d3fa7a304c7fcb99555","versionType":"git"},{"version":"e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c","status":"affected","lessThan":"b22dc0add7d72b8bd9cae3188db0dd65da1c8652","versionType":"git"},{"version":"e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c","status":"affected","lessThan":"891c21f6d5673b2a519b536243bfc6dd2d35beb6","versionType":"git"},{"version":"e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c","status":"affected","lessThan":"230234d12ce42ab04132a32c3a848f07a5d27a71","versionType":"git"},{"version":"8d505d06d7330f5d67d3e5e9e1c647fb0b10ddad","status":"affected","versionType":"git"},{"version":"6.1.33","status":"affected","lessThan":"6.1.189","versionType":"semver"},{"version":"6.3.7","status":"affected","lessThan":"6.4","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/trace_events_hist.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.4","versionType":"semver"},{"version":"6.1.189","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.111","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/trace_events_hist.c"]}],"references":["https://git.kernel.org/stable/c/a2652fcf96b63e9da04951e4e58e6a0672df695d","https://git.kernel.org/stable/c/3d42fed18b2c5707b6332ebe87b789fd768eb01b","https://git.kernel.org/stable/c/e787361bb6b0026ea3eb4d3fa7a304c7fcb99555","https://git.kernel.org/stable/c/b22dc0add7d72b8bd9cae3188db0dd65da1c8652","https://git.kernel.org/stable/c/891c21f6d5673b2a519b536243bfc6dd2d35beb6","https://git.kernel.org/stable/c/230234d12ce42ab04132a32c3a848f07a5d27a71"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/97xxx/CVE-2026-97921.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-97921","state":"PUBLISHED","datePublished":"2026-09-25T10:22:41.081Z","dateUpdated":"2026-10-19T09:10:48.148Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:18:58.202Z"},"containers":{"cna":{"title":"tracing: Free histogram the field rejected for a bad modifier","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Free histogram the field rejected for a bad modifier\n\nWriting a hist trigger whose value or variable carries a modifier that is\nnot allowed there leaks the fields that were built for it.\n\n__create_val_field() takes the field from parse_expr() and stores it in\nhist_data->fields[] only after the modifier checks have run:\n\n\thist_field = parse_expr(hist_data, file, field_str, flags, var_name,\n\t\t\t\t&n_subexprs);\n\t...\n\tif (hist_field->flags & HIST_FIELD_FL_VAR) {\n\t\tif (hist_field->flags & (...))\n\t\t\tgoto err;\n\t} else {\n\t\tif (hist_field->flags & (...))\n\t\t\tgoto err;\n\t}\n\n\thist_data->fields[val_idx] = hist_field;\n\nBoth checks jump past that store, and the err label returns without\nfreeing anything. The error unwinds to create_hist_data(), which calls\ndestroy_hist_data() -> destroy_hist_fields(), and that reaches a field\nonly by walking fields[]. A field that never got there is unreachable.\n\ncommit e0213434fe3e (\"tracing: Do not let histogram values have some\nmodifiers\") set ret to -EINVAL and fell through to the store, which left\nthe field owned by fields[] and freed along with the rest of hist_data.\nSplitting the check into a value case and a variable case replaced that\nfall-through with a goto that skips it.\n\nWith CONFIG_DEBUG_KMEMLEAK, 200 writes of\n\n  # echo 'hist:keys=prev_pid:vals=next_pid.log2' > \\\n\t events/sched/sched_switch/trigger\n\neach correctly rejected with -EINVAL, leave 332 unreferenced objects\n(63744 bytes) reported at create_hist_field(); 200 install and remove\ncycles of a valid trigger leave none. A '.log2' field is two\nallocations, since create_hist_field() puts the plain field in\noperands[0] of the log2 field, and both are reported.\n\nUse destroy_hist_field() rather than __destroy_hist_field() so that\noperands[0] is freed as well. It returns early for HIST_FIELD_FL_VAR_REF,\nwhich is what an operand owned by hist_data->var_refs[] needs; the\nrejected field itself is never a var ref, because a var ref never carries\na modifier flag."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"7403630eb94c1d664fb873f967427ef2f6ee3699","status":"affected","lessThan":"a2652fcf96b63e9da04951e4e58e6a0672df695d","versionType":"git"},{"version":"e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c","status":"affected","lessThan":"3d42fed18b2c5707b6332ebe87b789fd768eb01b","versionType":"git"},{"version":"e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c","status":"affected","lessThan":"e787361bb6b0026ea3eb4d3fa7a304c7fcb99555","versionType":"git"},{"version":"e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c","status":"affected","lessThan":"b22dc0add7d72b8bd9cae3188db0dd65da1c8652","versionType":"git"},{"version":"e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c","status":"affected","lessThan":"891c21f6d5673b2a519b536243bfc6dd2d35beb6","versionType":"git"},{"version":"e30fbc618e97b38dbb49f1d44dcd0778d3f23b8c","status":"affected","lessThan":"230234d12ce42ab04132a32c3a848f07a5d27a71","versionType":"git"},{"version":"8d505d06d7330f5d67d3e5e9e1c647fb0b10ddad","status":"affected","versionType":"git"},{"version":"6.1.33","status":"affected","lessThan":"6.1.189","versionType":"semver"},{"version":"6.3.7","status":"affected","lessThan":"6.4","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/trace_events_hist.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.4","versionType":"semver"},{"version":"6.1.189","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.111","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/trace_events_hist.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/a2652fcf96b63e9da04951e4e58e6a0672df695d"},{"url":"https://git.kernel.org/stable/c/3d42fed18b2c5707b6332ebe87b789fd768eb01b"},{"url":"https://git.kernel.org/stable/c/e787361bb6b0026ea3eb4d3fa7a304c7fcb99555"},{"url":"https://git.kernel.org/stable/c/b22dc0add7d72b8bd9cae3188db0dd65da1c8652"},{"url":"https://git.kernel.org/stable/c/891c21f6d5673b2a519b536243bfc6dd2d35beb6"},{"url":"https://git.kernel.org/stable/c/230234d12ce42ab04132a32c3a848f07a5d27a71"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:10:48.148Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.33","versionEndExcluding":"6.1.189"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.6.158"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.12.111"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.18.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.2.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.3"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.3.7"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}