From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions When using eBPF to probe CS CALL instructions within a function, a crash can be triggered. The eBPF tool probes offset 257 of the __hrtimer_run_queues() function: <__hrtimer_run_queues+249>: nopl 0x0(%rax,%rax,1) <__hrtimer_run_queues+254>: mov %r14,%rdi <__hrtimer_run_queues+257>: cs call <__x86_indirect_thunk_r12> <__hrtimer_run_queues+263>: mov %eax,%r12d <__hrtimer_run_queues+266>: xchg %ax,%ax <__hrtimer_run_queues+268>: mov %r13,%rdi Which triggers this crash: BUG: unable to handle page fault for address: 00000000000f41c9 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P RIP: 0010:__hrtimer_run_queues+0x106/0x230 Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is at the 6th byte of the above CS CALL instruction. Since the CS CALL instruction occupies 6 bytes, the exception occurred in the middle of that call instruction. The root cause is that when using eBPF tools to probe in the middle of a function, a kprobe with INT3 is used as the underlying implementation. During single-step emulation of the original CALL instruction, int3_emulate_call() assumes that the probed CALL instruction is 5 bytes long. However, the actual CS-prefixed CALL instruction occupies 6 bytes, so it constructs an incorrect exception return address. When the CPU returns from the kprobe handler, the next instruction to be executed is at the address of the last byte of that CS CALL instruction. Coincidentally, starting from that address, the CPU fetches and decodes a completely different instruction, which ultimately triggers a kernel crash. Fix the issue by using the actual instruction length obtained from the instruction decoder when constructing the exception return address, rather than relying on the hardcoded CALL_INSN_SIZE macro. [ mingo: Refined the changelog ] Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step") Suggested-by: Masami Hiramatsu (Google) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- fs/nfs_common/common.c | 200 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 200 insertions(+) create mode 100644 fs/nfs_common/common.c (limited to 'fs/nfs_common/common.c') diff --git a/fs/nfs_common/common.c b/fs/nfs_common/common.c new file mode 100644 index 000000000..0778743ae --- /dev/null +++ b/fs/nfs_common/common.c @@ -0,0 +1,200 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include +#include +#include + +/* + * We need to translate between nfs status return values and + * the local errno values which may not be the same. + */ +static const struct { + int stat; + int errno; +} nfs_errtbl[] = { + { NFS_OK, 0 }, + { NFSERR_PERM, -EPERM }, + { NFSERR_NOENT, -ENOENT }, + { NFSERR_IO, -EIO }, + { NFSERR_NXIO, -ENXIO }, + { NFSERR_ACCES, -EACCES }, + { NFSERR_EXIST, -EEXIST }, + { NFSERR_XDEV, -EXDEV }, + { NFSERR_NODEV, -ENODEV }, + { NFSERR_NOTDIR, -ENOTDIR }, + { NFSERR_ISDIR, -EISDIR }, + { NFSERR_INVAL, -EINVAL }, + { NFSERR_FBIG, -EFBIG }, + { NFSERR_NOSPC, -ENOSPC }, + { NFSERR_ROFS, -EROFS }, + { NFSERR_MLINK, -EMLINK }, + { NFSERR_NAMETOOLONG, -ENAMETOOLONG }, + { NFSERR_NOTEMPTY, -ENOTEMPTY }, + { NFSERR_DQUOT, -EDQUOT }, + { NFSERR_STALE, -ESTALE }, + { NFSERR_REMOTE, -EREMOTE }, +#ifdef EWFLUSH + { NFSERR_WFLUSH, -EWFLUSH }, +#endif + { NFSERR_BADHANDLE, -EBADHANDLE }, + { NFSERR_NOT_SYNC, -ENOTSYNC }, + { NFSERR_BAD_COOKIE, -EBADCOOKIE }, + { NFSERR_NOTSUPP, -ENOTSUPP }, + { NFSERR_TOOSMALL, -ETOOSMALL }, + { NFSERR_SERVERFAULT, -EREMOTEIO }, + { NFSERR_BADTYPE, -EBADTYPE }, + { NFSERR_JUKEBOX, -EJUKEBOX }, +}; + +/** + * nfs_stat_to_errno - convert an NFS status code to a local errno + * @status: NFS status code to convert + * + * Returns a local errno value, or -EIO if the NFS status code is + * not recognized. This function is used jointly by NFSv2 and NFSv3. + */ +int nfs_stat_to_errno(enum nfs_stat status) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(nfs_errtbl); i++) { + if (nfs_errtbl[i].stat == (int)status) + return nfs_errtbl[i].errno; + } + return -EIO; +} +EXPORT_SYMBOL_GPL(nfs_stat_to_errno); + +/* + * We need to translate between nfs v4 status return values and + * the local errno values which may not be the same. + * + * nfs4_errtbl_common[] is used before more specialized mappings + * available in nfs4_errtbl[] or nfs4_errtbl_localio[]. + */ +static const struct { + int stat; + int errno; +} nfs4_errtbl_common[] = { + { NFS4_OK, 0 }, + { NFS4ERR_PERM, -EPERM }, + { NFS4ERR_NOENT, -ENOENT }, + { NFS4ERR_IO, -EIO }, + { NFS4ERR_NXIO, -ENXIO }, + { NFS4ERR_ACCESS, -EACCES }, + { NFS4ERR_EXIST, -EEXIST }, + { NFS4ERR_XDEV, -EXDEV }, + { NFS4ERR_NOTDIR, -ENOTDIR }, + { NFS4ERR_ISDIR, -EISDIR }, + { NFS4ERR_INVAL, -EINVAL }, + { NFS4ERR_FBIG, -EFBIG }, + { NFS4ERR_NOSPC, -ENOSPC }, + { NFS4ERR_ROFS, -EROFS }, + { NFS4ERR_MLINK, -EMLINK }, + { NFS4ERR_NAMETOOLONG, -ENAMETOOLONG }, + { NFS4ERR_NOTEMPTY, -ENOTEMPTY }, + { NFS4ERR_DQUOT, -EDQUOT }, + { NFS4ERR_STALE, -ESTALE }, + { NFS4ERR_BADHANDLE, -EBADHANDLE }, + { NFS4ERR_BAD_COOKIE, -EBADCOOKIE }, + { NFS4ERR_NOTSUPP, -ENOTSUPP }, + { NFS4ERR_TOOSMALL, -ETOOSMALL }, + { NFS4ERR_BADTYPE, -EBADTYPE }, + { NFS4ERR_SYMLINK, -ELOOP }, + { NFS4ERR_DEADLOCK, -EDEADLK }, +}; + +static const struct { + int stat; + int errno; +} nfs4_errtbl[] = { + { NFS4ERR_SERVERFAULT, -EREMOTEIO }, + { NFS4ERR_LOCKED, -EAGAIN }, + { NFS4ERR_OP_ILLEGAL, -EOPNOTSUPP }, + { NFS4ERR_NOXATTR, -ENODATA }, + { NFS4ERR_XATTR2BIG, -E2BIG }, +}; + +/* + * Convert an NFS error code to a local one. + * This one is used by NFSv4. + */ +int nfs4_stat_to_errno(int stat) +{ + int i; + + /* First check nfs4_errtbl_common */ + for (i = 0; i < ARRAY_SIZE(nfs4_errtbl_common); i++) { + if (nfs4_errtbl_common[i].stat == stat) + return nfs4_errtbl_common[i].errno; + } + /* Then check nfs4_errtbl */ + for (i = 0; i < ARRAY_SIZE(nfs4_errtbl); i++) { + if (nfs4_errtbl[i].stat == stat) + return nfs4_errtbl[i].errno; + } + if (stat <= 10000 || stat > 10100) { + /* The server is looney tunes. */ + return -EREMOTEIO; + } + /* If we cannot translate the error, the recovery routines should + * handle it. + * Note: remaining NFSv4 error codes have values > 10000, so should + * not conflict with native Linux error codes. + */ + return -stat; +} +EXPORT_SYMBOL_GPL(nfs4_stat_to_errno); + +/* + * This table is useful for conversion from local errno to NFS error. + * It provides more logically correct mappings for use with LOCALIO + * (which is focused on converting from errno to NFS status). + */ +static const struct { + int stat; + int errno; +} nfs4_errtbl_localio[] = { + /* Map errors differently than nfs4_errtbl */ + { NFS4ERR_IO, -EREMOTEIO }, + { NFS4ERR_DELAY, -EAGAIN }, + { NFS4ERR_FBIG, -E2BIG }, + /* Map errors not handled by nfs4_errtbl */ + { NFS4ERR_STALE, -EBADF }, + { NFS4ERR_STALE, -EOPENSTALE }, + { NFS4ERR_DELAY, -ETIMEDOUT }, + { NFS4ERR_DELAY, -ERESTARTSYS }, + { NFS4ERR_DELAY, -ENOMEM }, + { NFS4ERR_IO, -ETXTBSY }, + { NFS4ERR_IO, -EBUSY }, + { NFS4ERR_SERVERFAULT, -ESERVERFAULT }, + { NFS4ERR_SERVERFAULT, -ENFILE }, + { NFS4ERR_IO, -EUCLEAN }, + { NFS4ERR_PERM, -ENOKEY }, +}; + +/* + * Convert an errno to an NFS error code for LOCALIO. + */ +__u32 nfs_localio_errno_to_nfs4_stat(int errno) +{ + int i; + + /* First check nfs4_errtbl_common */ + for (i = 0; i < ARRAY_SIZE(nfs4_errtbl_common); i++) { + if (nfs4_errtbl_common[i].errno == errno) + return nfs4_errtbl_common[i].stat; + } + /* Then check nfs4_errtbl_localio */ + for (i = 0; i < ARRAY_SIZE(nfs4_errtbl_localio); i++) { + if (nfs4_errtbl_localio[i].errno == errno) + return nfs4_errtbl_localio[i].stat; + } + /* If we cannot translate the error, the recovery routines should + * handle it. + * Note: remaining NFSv4 error codes have values > 10000, so should + * not conflict with native Linux error codes. + */ + return NFS4ERR_SERVERFAULT; +} +EXPORT_SYMBOL_GPL(nfs_localio_errno_to_nfs4_stat); -- cgit v1.3.1