Message-ID: <dc5b3808-6006-4eb1-baec-0b11c361db37@sirena.org.uk>
Date: Tue, 13 Jan 2026 15:31:14 +0000
From: Mark Brown <broonie@...nel.org>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: linux-fsdevel@...r.kernel.org, torvalds@...ux-foundation.org,
	brauner@...nel.org, jack@...e.cz, mjguzik@...il.com,
	paul@...l-moore.com, axboe@...nel.dk, audit@...r.kernel.org,
	io-uring@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 15/59] struct filename: saner handling of long names

On Thu, Jan 08, 2026 at 07:37:19AM +0000, Al Viro wrote:
> Always allocate struct filename from names_cachep, long name or short;
> short names would be embedded into struct filename.  Longer ones do
> not cannibalize the original struct filename - put them into kmalloc'ed
> buffers (PATH_MAX-sized for import from userland, strlen() + 1 - for
> ones originating kernel-side, where we know the length beforehand).

I'm seeing a regression in -next in the execveat kselftest which bisects
to 2a0db5f7653b ("struct filename: saner handling of long names").  The
test triggers two new failures with very long filenames for tests that
previously succeeded:

# # Failed to open length 4094 filename, errno=36 (File name too long)
# # Invoke exec via root_dfd and relative filename
# # child execveat() failed, rc=-1 errno=36 (File name too long)
# # child 9501 exited with 36 neither 99 nor 99
# not ok 48 Check success of execveat(8, 'opt/kselftest/exec/x...yyyyyyyyyyyyyyyyyyyy', 0)... 
# # Failed to open length 4094 filename, errno=36 (File name too long)
# # Invoke script via root_dfd and relative filename
# # child execveat() failed, rc=-1 errno=36 (File name too long)
# # child 9502 exited with 36 neither 127 nor 126
# not ok 49 Check success of execveat(8, 'opt/kselftest/exec/x...yyyyyyyyyyyyyyyyyyyy', 0)... 

full log:

   https://lava.sirena.org.uk/scheduler/job/2367409#L9827

bisect log with links to logs from other test runs:

# bad: [0f853ca2a798ead9d24d39cad99b0966815c582a] Add linux-next specific files for 20260113
# good: [9843d35ffaf3ffbc0e0a05cd36107fe6081e948e] Merge branch 'for-linux-next-fixes' of https://gitlab.freedesktop.org/drm/misc/kernel.git
# good: [77157cb45c66bd652a08a360693fcced558c5ef9] ASoC: codecs: rt1320-sdw: convert to snd_soc_dapm_xxx()
# good: [8d38423d9dea7353a8a54a3ab2e0d0aa04ed34d0] regulator: core: don't fail regulator_register() with missing required supply
# good: [b6376dbed8e173f9571583b5d358b08ff394e864] spi: Simplify devm_spi_*_controller()
# good: [0cd9bf6a6d9a1861087236cc5c275b3bea83cfdd] ASoC: codecs: da7213: Move comma operator at the end of the line
# good: [22a4776a9ce50aa47f602d28f53ba9d613a38f49] ASoC: codecs: es8375: remove unnecessary format check
# good: [75d208bddcca55ec31481420fbb4d6c9703ba195] spi: stm32: avoid __maybe_unused and use pm_ptr
# good: [04b61513dfe40f80f0dcc795003637b510522b3c] ASoC: SDCA: Replace use of system_wq with system_dfl_wq
# good: [9bf0bd7bdea6c402007ffb784dd0c0f704aa2310] ASoC: nau8821: Sort #include directives
# good: [96d337436fe0921177a6090aeb5bb214753654fc] spi: dt-bindings: at91: add microchip,lan9691-spi
# good: [211243b69533e968cc6f0259fb80ffee02fbe0ca] firmware: cs_dsp: test_bin: Add tests for offsets > 0xffff
# good: [52ddc0106c77ff0eacf07b309833ae6e6a4e8587] ASoC: es8328: Remove duplicate DAPM routes
# good: [4c5e6d5b31bc623d89185d551681ab91cfd037c9] ASoC: codecs: ES8389: Update clock configuration
# good: [420739112e95c9bb286b4e87875706925970abd3] ASoC: rt5575: Add the codec driver for the ALC5575
# good: [284853affe73fe1ca9786bd52b934eb9d420a942] ASoC: rt1320: fix size_t format string
# good: [25abdc151a448a17d500ea9468ce32582c479faa] ASoC: rt1320: fix the remainder calculation of r0 value
# good: [0f698d742f628d02ab2a222f8cf5f793443865d0] spi: bcm63xx-hsspi: add support for 1-2-2 read ops
# good: [45e9066f3a487e9e26b842644364d045af054775] ASoC: Intel: avs: replace strcmp with sysfs_streq
# good: [8db50f0fa43efe8799fd40b872dcdd39a90d7549] ASoC: rt1320: fix the warning the string may be truncated
# good: [c6bca73d699cfe00d3419566fdb2a45e112f44b0] ASoC: rt1320: Fix retry checking in rt1320_rae_load()
# good: [4ab48cc63e15cb619d641d1edf9a15a0a98875b2] ASoC: qcom: audioreach: Constify function arguments
# good: [99a3ef1e81cd1775bc1f8cc2ad188b1fc755d5cd] ASoC: SDCA: Add ASoC jack hookup in class driver
# good: [b0655377aa5a410df02d89170c20141a1a5bbc28] rust: regulator: replace `kernel::c_str!` with C-Strings
# good: [32a708ba5db50cf928a1f1b2039ceef33de2c286] regulator: Add rt8092 support
# good: [a2a631830deb382a3d27b6f52b2d654a3e6bb427] ASoC: qcom: Constify APR/GPR result structs
# good: [7a8447fc71a09000cee5a2372b6efde45735d2c8] ASoC: codecs: wcd939x-sdw: use devres for regmap allocation
# good: [b39ef93a2e5b5f4289a3486d8a94a09a1e6a4c67] spi: stm32: perform small transfer in polling mode
# good: [3622dc47a4b13e0ec86358c7b54a0b33bfcaa03c] ASoC: codec: rt286: Use devm_request_threaded_irq to manage IRQ lifetime and fix smatch warning
# good: [2a28b5240f2b328495c6565d277f438dbc583d61] ASoC: SOF: ipc4-control: Add support for generic bytes control
# good: [1303c2903889b01d581083ed92e439e7544dd3e5] MAINTAINERS: Add MAINTAINERS entry for the ATCSPI200 SPI controller driver
# good: [9a6bc0a406608e2520f18d996483c9d2e4a9fb27] ASoC: codecs: ES8326: Add kcontrol for DRE
# good: [29c8c00d9f9db5fb659b6f05f9e8964afc13f3e2] spi: add driver for NXP XSPI controller
# good: [7f7b350e4a65446f5d52ea8ae99e12eac8a972db] spi: stm32-qspi: Remove unneeded semicolon
# good: [02e7af5b6423d2dbf82f852572f2fa8c00aafb19] ASoC: Intel: sof_rt5682: add tas2563 speaker amp support
# good: [f764645cb85a8b8f58067289cdfed28f6c1cdf49] ASoC: codecs: tas2780: tidyup format check in tas2780_set_fmt()
# good: [f4acea9eef704607d1a950909ce3a52a770d6be2] spi: dt-bindings: st,stm32-spi: add 'power-domains' property
# good: [f25c7d709b93602ee9a08eba522808a18e1f5d56] ASoC: SOF: Intel: pci-nvl: Set on_demand_dsp_boot for NVL-S
# good: [524ee559948d8d079b13466e70fa741f909699c0] ASoC: SOF: Intel: hda: Only check SSP MCLK mask in case of IPC3
# good: [aa30193af8873b3ccfd70a4275336ab6cbd4e5e6] ASoC: Intel: catpt: Drop superfluous space in PCM code
# good: [e39011184f23de3d04ca8e80b4df76c9047b4026] ASoC: SDCA: functions: Fix confusing cleanup.h syntax
# good: [03d281f384768610bf90697bce9e35d3d596de77] rust: regulator: add __rust_helper to helpers
# good: [ba9b28652c75b07383e267328f1759195d5430f7] spi: imx: enable DMA mode for target operation
# good: [9e92c559d49d6fb903af17a31a469aac51b1766d] regulator: max77675: Add MAX77675 regulator driver
# good: [81acbdc51bbbec822a1525481f2f70677c47aee0] ASoC: sdw-mockup: Drop dummy remove function
# good: [b884e34994ca41f7b7819f3c41b78ff494787b27] spi: spi-fsl-lpspi: convert min_t() to simple min()
# good: [fa08b566860bca8ebf9300090b85174c34de7ca5] spi: rzv2h-rspi: add support for DMA mode
# good: [0bb160c92ad400c692984763996b758458adea17] ASoC: qcom: Minor readability improve with new lines
# good: [fee876b2ec75dcc18fdea154eae1f5bf14d82659] spi: stm32-qspi: Simplify SMIE interrupt test
# good: [124f6155f3d97b0e33f178c10a5138a42c8fd207] ASoC: renesas: rz-ssi: Add support for 32 bits sample width
git bisect start '0f853ca2a798ead9d24d39cad99b0966815c582a' '9843d35ffaf3ffbc0e0a05cd36107fe6081e948e' '77157cb45c66bd652a08a360693fcced558c5ef9' '8d38423d9dea7353a8a54a3ab2e0d0aa04ed34d0' 'b6376dbed8e173f9571583b5d358b08ff394e864' '0cd9bf6a6d9a1861087236cc5c275b3bea83cfdd' '22a4776a9ce50aa47f602d28f53ba9d613a38f49' '75d208bddcca55ec31481420fbb4d6c9703ba195' '04b61513dfe40f80f0dcc795003637b510522b3c' '9bf0bd7bdea6c402007ffb784dd0c0f704aa2310' '96d337436fe0921177a6090aeb5bb214753654fc' '211243b69533e968cc6f0259fb80ffee02fbe0ca' '52ddc0106c77ff0eacf07b309833ae6e6a4e8587' '4c5e6d5b31bc623d89185d551681ab91cfd037c9' '420739112e95c9bb286b4e87875706925970abd3' '284853affe73fe1ca9786bd52b934eb9d420a942' '25abdc151a448a17d500ea9468ce32582c479faa' '0f698d742f628d02ab2a222f8cf5f793443865d0' '45e9066f3a487e9e26b842644364d045af054775' '8db50f0fa43efe8799fd40b872dcdd39a90d7549' 'c6bca73d699cfe00d3419566fdb2a45e112f44b0' '4ab48cc63e15cb619d641d1edf9a15a0a98875b2' '99a3ef1e81cd1775bc1f8cc2ad188b1fc755d5cd' 'b0655377aa5a410df02d89170c20141a1a5bbc28' '32a708ba5db50cf928a1f1b2039ceef33de2c286' 'a2a631830deb382a3d27b6f52b2d654a3e6bb427' '7a8447fc71a09000cee5a2372b6efde45735d2c8' 'b39ef93a2e5b5f4289a3486d8a94a09a1e6a4c67' '3622dc47a4b13e0ec86358c7b54a0b33bfcaa03c' '2a28b5240f2b328495c6565d277f438dbc583d61' '1303c2903889b01d581083ed92e439e7544dd3e5' '9a6bc0a406608e2520f18d996483c9d2e4a9fb27' '29c8c00d9f9db5fb659b6f05f9e8964afc13f3e2' '7f7b350e4a65446f5d52ea8ae99e12eac8a972db' '02e7af5b6423d2dbf82f852572f2fa8c00aafb19' 'f764645cb85a8b8f58067289cdfed28f6c1cdf49' 'f4acea9eef704607d1a950909ce3a52a770d6be2' 'f25c7d709b93602ee9a08eba522808a18e1f5d56' '524ee559948d8d079b13466e70fa741f909699c0' 'aa30193af8873b3ccfd70a4275336ab6cbd4e5e6' 'e39011184f23de3d04ca8e80b4df76c9047b4026' '03d281f384768610bf90697bce9e35d3d596de77' 'ba9b28652c75b07383e267328f1759195d5430f7' '9e92c559d49d6fb903af17a31a469aac51b1766d' '81acbdc51bbbec822a1525481f2f70677c47aee0' 'b884e34994ca41f7b7819f3c41b78ff494787b27' 'fa08b566860bca8ebf9300090b85174c34de7ca5' '0bb160c92ad400c692984763996b758458adea17' 'fee876b2ec75dcc18fdea154eae1f5bf14d82659' '124f6155f3d97b0e33f178c10a5138a42c8fd207'
# test job: [77157cb45c66bd652a08a360693fcced558c5ef9] https://lava.sirena.org.uk/scheduler/job/2363772
# test job: [8d38423d9dea7353a8a54a3ab2e0d0aa04ed34d0] https://lava.sirena.org.uk/scheduler/job/2354346
# test job: [b6376dbed8e173f9571583b5d358b08ff394e864] https://lava.sirena.org.uk/scheduler/job/2349564
# test job: [0cd9bf6a6d9a1861087236cc5c275b3bea83cfdd] https://lava.sirena.org.uk/scheduler/job/2348760
# test job: [22a4776a9ce50aa47f602d28f53ba9d613a38f49] https://lava.sirena.org.uk/scheduler/job/2344104
# test job: [75d208bddcca55ec31481420fbb4d6c9703ba195] https://lava.sirena.org.uk/scheduler/job/2337439
# test job: [04b61513dfe40f80f0dcc795003637b510522b3c] https://lava.sirena.org.uk/scheduler/job/2337708
# test job: [9bf0bd7bdea6c402007ffb784dd0c0f704aa2310] https://lava.sirena.org.uk/scheduler/job/2331106
# test job: [96d337436fe0921177a6090aeb5bb214753654fc] https://lava.sirena.org.uk/scheduler/job/2330456
# test job: [211243b69533e968cc6f0259fb80ffee02fbe0ca] https://lava.sirena.org.uk/scheduler/job/2330728
# test job: [52ddc0106c77ff0eacf07b309833ae6e6a4e8587] https://lava.sirena.org.uk/scheduler/job/2331457
# test job: [4c5e6d5b31bc623d89185d551681ab91cfd037c9] https://lava.sirena.org.uk/scheduler/job/2331902
# test job: [420739112e95c9bb286b4e87875706925970abd3] https://lava.sirena.org.uk/scheduler/job/2331721
# test job: [284853affe73fe1ca9786bd52b934eb9d420a942] https://lava.sirena.org.uk/scheduler/job/2298053
# test job: [25abdc151a448a17d500ea9468ce32582c479faa] https://lava.sirena.org.uk/scheduler/job/2307389
# test job: [0f698d742f628d02ab2a222f8cf5f793443865d0] https://lava.sirena.org.uk/scheduler/job/2295213
# test job: [45e9066f3a487e9e26b842644364d045af054775] https://lava.sirena.org.uk/scheduler/job/2295673
# test job: [8db50f0fa43efe8799fd40b872dcdd39a90d7549] https://lava.sirena.org.uk/scheduler/job/2292101
# test job: [c6bca73d699cfe00d3419566fdb2a45e112f44b0] https://lava.sirena.org.uk/scheduler/job/2290170
# test job: [4ab48cc63e15cb619d641d1edf9a15a0a98875b2] https://lava.sirena.org.uk/scheduler/job/2290906
# test job: [99a3ef1e81cd1775bc1f8cc2ad188b1fc755d5cd] https://lava.sirena.org.uk/scheduler/job/2290884
# test job: [b0655377aa5a410df02d89170c20141a1a5bbc28] https://lava.sirena.org.uk/scheduler/job/2291654
# test job: [32a708ba5db50cf928a1f1b2039ceef33de2c286] https://lava.sirena.org.uk/scheduler/job/2279424
# test job: [a2a631830deb382a3d27b6f52b2d654a3e6bb427] https://lava.sirena.org.uk/scheduler/job/2281855
# test job: [7a8447fc71a09000cee5a2372b6efde45735d2c8] https://lava.sirena.org.uk/scheduler/job/2271765
# test job: [b39ef93a2e5b5f4289a3486d8a94a09a1e6a4c67] https://lava.sirena.org.uk/scheduler/job/2269645
# test job: [3622dc47a4b13e0ec86358c7b54a0b33bfcaa03c] https://lava.sirena.org.uk/scheduler/job/2268634
# test job: [2a28b5240f2b328495c6565d277f438dbc583d61] https://lava.sirena.org.uk/scheduler/job/2266207
# test job: [1303c2903889b01d581083ed92e439e7544dd3e5] https://lava.sirena.org.uk/scheduler/job/2263475
# test job: [9a6bc0a406608e2520f18d996483c9d2e4a9fb27] https://lava.sirena.org.uk/scheduler/job/2264400
# test job: [29c8c00d9f9db5fb659b6f05f9e8964afc13f3e2] https://lava.sirena.org.uk/scheduler/job/2263994
# test job: [7f7b350e4a65446f5d52ea8ae99e12eac8a972db] https://lava.sirena.org.uk/scheduler/job/2268219
# test job: [02e7af5b6423d2dbf82f852572f2fa8c00aafb19] https://lava.sirena.org.uk/scheduler/job/2262640
# test job: [f764645cb85a8b8f58067289cdfed28f6c1cdf49] https://lava.sirena.org.uk/scheduler/job/2264492
# test job: [f4acea9eef704607d1a950909ce3a52a770d6be2] https://lava.sirena.org.uk/scheduler/job/2243888
# test job: [f25c7d709b93602ee9a08eba522808a18e1f5d56] https://lava.sirena.org.uk/scheduler/job/2244120
# test job: [524ee559948d8d079b13466e70fa741f909699c0] https://lava.sirena.org.uk/scheduler/job/2243989
# test job: [aa30193af8873b3ccfd70a4275336ab6cbd4e5e6] https://lava.sirena.org.uk/scheduler/job/2232727
# test job: [e39011184f23de3d04ca8e80b4df76c9047b4026] https://lava.sirena.org.uk/scheduler/job/2232430
# test job: [03d281f384768610bf90697bce9e35d3d596de77] https://lava.sirena.org.uk/scheduler/job/2231119
# test job: [ba9b28652c75b07383e267328f1759195d5430f7] https://lava.sirena.org.uk/scheduler/job/2231400
# test job: [9e92c559d49d6fb903af17a31a469aac51b1766d] https://lava.sirena.org.uk/scheduler/job/2232511
# test job: [81acbdc51bbbec822a1525481f2f70677c47aee0] https://lava.sirena.org.uk/scheduler/job/2232850
# test job: [b884e34994ca41f7b7819f3c41b78ff494787b27] https://lava.sirena.org.uk/scheduler/job/2232571
# test job: [fa08b566860bca8ebf9300090b85174c34de7ca5] https://lava.sirena.org.uk/scheduler/job/2232948
# test job: [0bb160c92ad400c692984763996b758458adea17] https://lava.sirena.org.uk/scheduler/job/2233041
# test job: [fee876b2ec75dcc18fdea154eae1f5bf14d82659] https://lava.sirena.org.uk/scheduler/job/2231262
# test job: [124f6155f3d97b0e33f178c10a5138a42c8fd207] https://lava.sirena.org.uk/scheduler/job/2232864
# test job: [0f853ca2a798ead9d24d39cad99b0966815c582a] https://lava.sirena.org.uk/scheduler/job/2367409
# bad: [0f853ca2a798ead9d24d39cad99b0966815c582a] Add linux-next specific files for 20260113
git bisect bad 0f853ca2a798ead9d24d39cad99b0966815c582a
# test job: [80f60a6b0c1e21da3f74ede4c74aa3f38efa31d5] https://lava.sirena.org.uk/scheduler/job/2367513
# bad: [80f60a6b0c1e21da3f74ede4c74aa3f38efa31d5] Merge branch 'libcrypto-next' of https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git
git bisect bad 80f60a6b0c1e21da3f74ede4c74aa3f38efa31d5
# test job: [a0be739e9567908ff7b1b5efcc1c6b1f9e55a544] https://lava.sirena.org.uk/scheduler/job/2367625
# good: [a0be739e9567908ff7b1b5efcc1c6b1f9e55a544] Merge branch 'next' of https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git
git bisect good a0be739e9567908ff7b1b5efcc1c6b1f9e55a544
# test job: [50557224aa7b79cd076b9bb017a8b30e6b879b3f] https://lava.sirena.org.uk/scheduler/job/2367737
# bad: [50557224aa7b79cd076b9bb017a8b30e6b879b3f] Merge branch 'docs-next' of git://git.lwn.net/linux.git
git bisect bad 50557224aa7b79cd076b9bb017a8b30e6b879b3f
# test job: [7ff8a8def75f2b640b88af58a4b12a4882374ce8] https://lava.sirena.org.uk/scheduler/job/2367846
# good: [7ff8a8def75f2b640b88af58a4b12a4882374ce8] Merge branch 'vfs.all' of https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
git bisect good 7ff8a8def75f2b640b88af58a4b12a4882374ce8
# test job: [19513ff202450d2ccc5fdbb202450af78ac21006] https://lava.sirena.org.uk/scheduler/job/2367991
# bad: [19513ff202450d2ccc5fdbb202450af78ac21006] Merge branch 'next' of https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git
git bisect bad 19513ff202450d2ccc5fdbb202450af78ac21006
# test job: [3b4263ecddfdcf6c32339ede719b5071159e56ef] https://lava.sirena.org.uk/scheduler/job/2368112
# good: [3b4263ecddfdcf6c32339ede719b5071159e56ef] Merge branch 'pci/controller/misc'
git bisect good 3b4263ecddfdcf6c32339ede719b5071159e56ef
# test job: [732d43b6978db54024283dcd013e17064003f0d9] https://lava.sirena.org.uk/scheduler/job/2368208
# bad: [732d43b6978db54024283dcd013e17064003f0d9] do_sys_truncate(): switch to CLASS(filename)
git bisect bad 732d43b6978db54024283dcd013e17064003f0d9
# test job: [46c4e9f4ebbddda1f4c37355dafcd4f10400a4ca] https://lava.sirena.org.uk/scheduler/job/2368283
# bad: [46c4e9f4ebbddda1f4c37355dafcd4f10400a4ca] file_getattr(): filename_lookup() accepts ERR_PTR() as filename
git bisect bad 46c4e9f4ebbddda1f4c37355dafcd4f10400a4ca
# test job: [2e0ee29dc2414f63503b79968a5081d8bffe00d2] https://lava.sirena.org.uk/scheduler/job/2368364
# good: [2e0ee29dc2414f63503b79968a5081d8bffe00d2] get rid of audit_reusename()
git bisect good 2e0ee29dc2414f63503b79968a5081d8bffe00d2
# test job: [2a0db5f7653b3576c430f8821654f365aaa7f178] https://lava.sirena.org.uk/scheduler/job/2368516
# bad: [2a0db5f7653b3576c430f8821654f365aaa7f178] struct filename: saner handling of long names
git bisect bad 2a0db5f7653b3576c430f8821654f365aaa7f178
# test job: [9700b822564a7f22137f3017951b1540b98d0278] https://lava.sirena.org.uk/scheduler/job/2368899
# good: [9700b822564a7f22137f3017951b1540b98d0278] getname_flags() massage, part 1
git bisect good 9700b822564a7f22137f3017951b1540b98d0278
# test job: [25d18822f3d92a78f38a4fb32c8ff1d9a28f6072] https://lava.sirena.org.uk/scheduler/job/2369056
# good: [25d18822f3d92a78f38a4fb32c8ff1d9a28f6072] struct filename: use names_cachep only for getname() and friends
git bisect good 25d18822f3d92a78f38a4fb32c8ff1d9a28f6072
# first bad commit: [2a0db5f7653b3576c430f8821654f365aaa7f178] struct filename: saner handling of long names

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