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Larysa Zaremba 98cd8b4d0b xdp: produce a warning when calculated tailroom is negative 
[ Upstream commit 8821e85775 ]

Many ethernet drivers report xdp Rx queue frag size as being the same as
DMA write size. However, the only user of this field, namely
bpf_xdp_frags_increase_tail(), clearly expects a truesize.

Such difference leads to unspecific memory corruption issues under certain
circumstances, e.g. in ixgbevf maximum DMA write size is 3 KB, so when
running xskxceiver's XDP_ADJUST_TAIL_GROW_MULTI_BUFF, 6K packet fully uses
all DMA-writable space in 2 buffers. This would be fine, if only
rxq->frag_size was properly set to 4K, but value of 3K results in a
negative tailroom, because there is a non-zero page offset.

We are supposed to return -EINVAL and be done with it in such case, but due
to tailroom being stored as an unsigned int, it is reported to be somewhere
near UINT_MAX, resulting in a tail being grown, even if the requested
offset is too much (it is around 2K in the abovementioned test). This later
leads to all kinds of unspecific calltraces.

[ 7340.337579] xskxceiver[1440]: segfault at 1da718 ip 00007f4161aeac9d sp 00007f41615a6a00 error 6
[ 7340.338040] xskxceiver[1441]: segfault at 7f410000000b ip 00000000004042b5 sp 00007f415bffecf0 error 4
[ 7340.338179]  in libc.so.6[61c9d,7f4161aaf000+160000]
[ 7340.339230]  in xskxceiver[42b5,400000+69000]
[ 7340.340300]  likely on CPU 6 (core 0, socket 6)
[ 7340.340302] Code: ff ff 01 e9 f4 fe ff ff 0f 1f 44 00 00 4c 39 f0 74 73 31 c0 ba 01 00 00 00 f0 0f b1 17 0f 85 ba 00 00 00 49 8b 87 88 00 00 00 <4c> 89 70 08 eb cc 0f 1f 44 00 00 48 8d bd f0 fe ff ff 89 85 ec fe
[ 7340.340888]  likely on CPU 3 (core 0, socket 3)
[ 7340.345088] Code: 00 00 00 ba 00 00 00 00 be 00 00 00 00 89 c7 e8 31 ca ff ff 89 45 ec 8b 45 ec 85 c0 78 07 b8 00 00 00 00 eb 46 e8 0b c8 ff ff <8b> 00 83 f8 69 74 24 e8 ff c7 ff ff 8b 00 83 f8 0b 74 18 e8 f3 c7
[ 7340.404334] Oops: general protection fault, probably for non-canonical address 0x6d255010bdffc: 0000 [#1] SMP NOPTI
[ 7340.405972] CPU: 7 UID: 0 PID: 1439 Comm: xskxceiver Not tainted 6.19.0-rc1+ #21 PREEMPT(lazy)
[ 7340.408006] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-5.fc42 04/01/2014
[ 7340.409716] RIP: 0010:lookup_swap_cgroup_id+0x44/0x80
[ 7340.410455] Code: 83 f8 1c 73 39 48 ba ff ff ff ff ff ff ff 03 48 8b 04 c5 20 55 fa bd 48 21 d1 48 89 ca 83 e1 01 48 d1 ea c1 e1 04 48 8d 04 90 <8b> 00 48 83 c4 10 d3 e8 c3 cc cc cc cc 31 c0 e9 98 b7 dd 00 48 89
[ 7340.412787] RSP: 0018:ffffcc5c04f7f6d0 EFLAGS: 00010202
[ 7340.413494] RAX: 0006d255010bdffc RBX: ffff891f477895a8 RCX: 0000000000000010
[ 7340.414431] RDX: 0001c17e3fffffff RSI: 00fa070000000000 RDI: 000382fc7fffffff
[ 7340.415354] RBP: 00fa070000000000 R08: ffffcc5c04f7f8f8 R09: ffffcc5c04f7f7d0
[ 7340.416283] R10: ffff891f4c1a7000 R11: ffffcc5c04f7f9c8 R12: ffffcc5c04f7f7d0
[ 7340.417218] R13: 03ffffffffffffff R14: 00fa06fffffffe00 R15: ffff891f47789500
[ 7340.418229] FS:  0000000000000000(0000) GS:ffff891ffdfaa000(0000) knlGS:0000000000000000
[ 7340.419489] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 7340.420286] CR2: 00007f415bfffd58 CR3: 0000000103f03002 CR4: 0000000000772ef0
[ 7340.421237] PKRU: 55555554
[ 7340.421623] Call Trace:
[ 7340.421987]  <TASK>
[ 7340.422309]  ? softleaf_from_pte+0x77/0xa0
[ 7340.422855]  swap_pte_batch+0xa7/0x290
[ 7340.423363]  zap_nonpresent_ptes.constprop.0.isra.0+0xd1/0x270
[ 7340.424102]  zap_pte_range+0x281/0x580
[ 7340.424607]  zap_pmd_range.isra.0+0xc9/0x240
[ 7340.425177]  unmap_page_range+0x24d/0x420
[ 7340.425714]  unmap_vmas+0xa1/0x180
[ 7340.426185]  exit_mmap+0xe1/0x3b0
[ 7340.426644]  __mmput+0x41/0x150
[ 7340.427098]  exit_mm+0xb1/0x110
[ 7340.427539]  do_exit+0x1b2/0x460
[ 7340.427992]  do_group_exit+0x2d/0xc0
[ 7340.428477]  get_signal+0x79d/0x7e0
[ 7340.428957]  arch_do_signal_or_restart+0x34/0x100
[ 7340.429571]  exit_to_user_mode_loop+0x8e/0x4c0
[ 7340.430159]  do_syscall_64+0x188/0x6b0
[ 7340.430672]  ? __do_sys_clone3+0xd9/0x120
[ 7340.431212]  ? switch_fpu_return+0x4e/0xd0
[ 7340.431761]  ? arch_exit_to_user_mode_prepare.isra.0+0xa1/0xc0
[ 7340.432498]  ? do_syscall_64+0xbb/0x6b0
[ 7340.433015]  ? __handle_mm_fault+0x445/0x690
[ 7340.433582]  ? count_memcg_events+0xd6/0x210
[ 7340.434151]  ? handle_mm_fault+0x212/0x340
[ 7340.434697]  ? do_user_addr_fault+0x2b4/0x7b0
[ 7340.435271]  ? clear_bhb_loop+0x30/0x80
[ 7340.435788]  ? clear_bhb_loop+0x30/0x80
[ 7340.436299]  ? clear_bhb_loop+0x30/0x80
[ 7340.436812]  ? clear_bhb_loop+0x30/0x80
[ 7340.437323]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 7340.437973] RIP: 0033:0x7f4161b14169
[ 7340.438468] Code: Unable to access opcode bytes at 0x7f4161b1413f.
[ 7340.439242] RSP: 002b:00007ffc6ebfa770 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
[ 7340.440173] RAX: fffffffffffffe00 RBX: 00000000000005a1 RCX: 00007f4161b14169
[ 7340.441061] RDX: 00000000000005a1 RSI: 0000000000000109 RDI: 00007f415bfff990
[ 7340.441943] RBP: 00007ffc6ebfa7a0 R08: 0000000000000000 R09: 00000000ffffffff
[ 7340.442824] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
[ 7340.443707] R13: 0000000000000000 R14: 00007f415bfff990 R15: 00007f415bfff6c0
[ 7340.444586]  </TASK>
[ 7340.444922] Modules linked in: rfkill intel_rapl_msr intel_rapl_common intel_uncore_frequency_common skx_edac_common nfit libnvdimm kvm_intel vfat fat kvm snd_pcm irqbypass rapl iTCO_wdt snd_timer intel_pmc_bxt iTCO_vendor_support snd ixgbevf virtio_net soundcore i2c_i801 pcspkr libeth_xdp net_failover i2c_smbus lpc_ich failover libeth virtio_balloon joydev 9p fuse loop zram lz4hc_compress lz4_compress 9pnet_virtio 9pnet netfs ghash_clmulni_intel serio_raw qemu_fw_cfg
[ 7340.449650] ---[ end trace 0000000000000000 ]---

The issue can be fixed in all in-tree drivers, but we cannot just trust OOT
drivers to not do this. Therefore, make tailroom a signed int and produce a
warning when it is negative to prevent such mistakes in the future.

Fixes: bf25146a55 ("bpf: add frags support to the bpf_xdp_adjust_tail() API")
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
Link: https://patch.msgid.link/20260305111253.2317394-10-larysa.zaremba@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-03-12 07:10:02 -04:00
arch ARM: clean up the memset64() C wrapper 2026-03-12 07:09:44 -04:00
block block: use trylock to avoid lockdep circular dependency in sysfs 2026-03-12 07:09:59 -04:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-30 10:32:12 +01:00
Documentation hwmon: (aht10) Add support for dht20 2026-03-12 07:09:46 -04:00
drivers net: enetc: use truesize as XDP RxQ info frag_size 2026-03-12 07:10:02 -04:00
fs smb/client: fix buffer size for smb311_posix_qinfo in SMB311_posix_query_info() 2026-03-12 07:09:56 -04:00
include xsk: introduce helper to determine rxq->frag_size 2026-03-12 07:10:01 -04:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/zcrx: fix user_ref race between scrub and refill paths 2026-03-04 07:21:33 -05:00
ipc ipc: don't audit capability check in ipc_permissions() 2026-02-26 14:59:19 -08:00
kernel timekeeping: Fix timex status validation for auxiliary clocks 2026-03-12 07:09:57 -04:00
lib debugobject: Make it work with deferred page initialization - again 2026-03-12 07:09:08 -04:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm: thp: deny THP for files on anonymous inodes 2026-03-12 07:09:41 -04:00
net xdp: produce a warning when calculated tailroom is negative 2026-03-12 07:10:02 -04:00
rust rust: kunit: fix warning when !CONFIG_PRINTK 2026-03-12 07:09:52 -04:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:17:11 +01:00
scripts kbuild: rpm-pkg: Disable automatic requires for manual debuginfo package 2026-03-04 07:21:32 -05:00
security ima: verify the previous kernel's IMA buffer lies in addressable RAM 2026-03-04 07:21:17 -05:00
sound ASoC: fsl_xcvr: provide regmap names 2026-03-12 07:09:44 -04:00
tools selftests/harness: order TEST_F and XFAIL_ADD constructors 2026-03-12 07:10:00 -04:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:41:44 +01:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.16 2026-03-04 07:25:12 -05:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.