CVE-2024-50067: uprobe: avoid out-of-bounds memory access of fetching args

In the Linux kernel, the following vulnerability has been resolved:

uprobe: avoid out-of-bounds memory access of fetching args

Uprobe needs to fetch args into a percpu buffer, and then copy to ring buffer to avoid non-atomic context problem.

Sometimes user-space strings, arrays can be very large, but the size of percpu buffer is only page size. And storetraceargs() won't check whether these data exceeds a single page or not, caused out-of-bounds memory access.

It could be reproduced by following steps: 1. build kernel with CONFIGKASAN enabled 2. save follow program as test.c

\#include <stdio.h> \#include <stdlib.h> \#include <string.h>

// If string length large than MAXSTRINGSIZE, the fetchstorestrlen() // will return 0, cause getdatasize() return shorter size, and // storetraceargs() will not trigger out-of-bounds access. // So make string length less than 4096. \#define STRLEN 4093

void generatestring(char str, int n) { int i; for (i = 0; i < n; ++i) { char c = i % 26 + 'a'; str[i] = c; } str[n-1] = '\0'; }

void printstring(char str) { printf("%s\n", str); }

int main() { char tmp[STRLEN];

generatestring(tmp, STRLEN); printstring(tmp);

return 0; } 3. compile program gcc -o test test.c

4. get the offset of printstring() objdump -t test | grep -w printstring 0000000000401199 g F .text 000000000000001b printstring

5. configure uprobe with offset 0x1199 off=0x1199

cd /sys/kernel/debug/tracing/ echo "p /root/test:${off} arg1=+0(%di):ustring arg2=\$comm arg3=+0(%di):ustring" > uprobeevents echo 1 > events/uprobes/enable echo 1 > tracingon

6. run test, and kasan will report error. ================================================================== BUG: KASAN: use-after-free in strncpyfromuser+0x1d6/0x1f0 Write of size 8 at addr ffff88812311c004 by task test/499CPU: 0 UID: 0 PID: 499 Comm: test Not tainted 6.12.0-rc3+ #18 Hardware name: Red Hat KVM, BIOS 1.16.0-4.al8 04/01/2014 Call Trace: <TASK> dumpstacklvl+0x55/0x70 printaddressdescription.constprop.0+0x27/0x310 kasanreport+0x10f/0x120 ? strncpyfromuser+0x1d6/0x1f0 strncpyfromuser+0x1d6/0x1f0 ? rmqueue.constprop.0+0x70d/0x2ad0 processfetchinsn+0xb26/0x1470 ? pfxprocessfetchinsn+0x10/0x10 ? rawspinlock+0x85/0xe0 ? pfxrawspinlock+0x10/0x10 ? pteoffsetmap+0x1f/0x2d0 ? unwindnextframe+0xc5f/0x1f80 ? archstackwalk+0x68/0xf0 ? isbpftextaddress+0x23/0x30 ? kerneltextaddress.part.0+0xbb/0xd0 ? kerneltextaddress+0x66/0xb0 ? unwindgetreturnaddress+0x5e/0xa0 ? pfxstacktraceconsumeentry+0x10/0x10 ? archstackwalk+0xa2/0xf0 ? rawspinlockirqsave+0x8b/0xf0 ? pfxrawspinlockirqsave+0x10/0x10 ? depotallocstack+0x4c/0x1f0 ? rawspinunlockirqrestore+0xe/0x30 ? stackdepotsaveflags+0x35d/0x4f0 ? kasansavestack+0x34/0x50 ? kasansavestack+0x24/0x50 ? mutexlock+0x91/0xe0 ? pfxmutexlock+0x10/0x10 prepareuprobebuffer.part.0+0x2cd/0x500 uprobedispatcher+0x2c3/0x6a0 ? pfxuprobedispatcher+0x10/0x10 ? kasanslaballoc+0x4d/0x90 handlerchain+0xdd/0x3e0 handleswbp+0x26e/0x3d0 ? pfxhandleswbp+0x10/0x10 ? uprobepresstepnotifier+0x151/0x1b0 irqentryexittousermode+0xe2/0x1b0 asmexcint3+0x39/0x40 RIP: 0033:0x401199 Code: 01 c2 0f b6 45 fb 88 02 83 45 fc 01 8b 45 fc 3b 45 e4 7c b7 8b 45 e4 48 98 48 8d 50 ff 48 8b 45 e8 48 01 d0 ce RSP: 002b:00007ffdf00576a8 EFLAGS: 00000206 RAX: 00007ffdf00576b0 RBX: 0000000000000000 RCX: 0000000000000ff2 RDX: 0000000000000ffc RSI: 0000000000000ffd RDI: 00007ffdf00576b0 RBP: 00007ffdf00586b0 R08: 00007feb2f9c0d20 R09: 00007feb2f9c0d20 R10: 0000000000000001 R11: 0000000000000202 R12: 0000000000401040 R13: 00007ffdf0058780 R14: 0000000000000000 R15: 0000000000000000 </TASK>

This commit enforces the buffer's maxlen less than a page-size to avoid storetraceargs() out-of-memory access.