On Mon, 24 Jan 2022 at 12:42, Vegard Nossum <vegard.nossum@xxxxxxxxx> wrote: > > On Thu, 20 Jan 2022 at 15:17, syzbot > <syzbot+5027de09e0964fd78ce1@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > > > syzbot suspects this issue was fixed by commit: > > > > commit 218d747a4142f281a256687bb513a135c905867b > > Author: John Fastabend <john.fastabend@xxxxxxxxx> > > Date: Tue Jan 4 21:46:45 2022 +0000 > > > > bpf, sockmap: Fix double bpf_prog_put on error case in map_link > > I can confirm the above commit fixes the issue, but it references a > slightly different report. Looks like the only difference is > __bpf_prog_put instead of bpf_prog_put: > > KASAN: vmalloc-out-of-bounds Read in __bpf_prog_put > KASAN: vmalloc-out-of-bounds Read in bpf_prog_put > > However, looking at the stack traces for the two bugs shows that > __bpf_prog_put() is really the location for both reports, see: > > https://syzkaller.appspot.com/bug?id=797cd651dd0d9bd921e4fa51b792f5afdc3f390f > kasan_report.cold+0x83/0xdf mm/kasan/report.c:450 mm/kasan/report.c:450 > __bpf_prog_put.constprop.0+0x1dd/0x220 kernel/bpf/syscall.c:1812 > kernel/bpf/syscall.c:1812 > bpf_prog_put kernel/bpf/syscall.c:1829 [inline] > bpf_prog_put kernel/bpf/syscall.c:1829 [inline] kernel/bpf/syscall.c:1837 > > vs. > > https://syzkaller.appspot.com/bug?extid=bb73e71cf4b8fd376a4f > kasan_report+0x19a/0x1f0 mm/kasan/report.c:450 mm/kasan/report.c:450 > __bpf_prog_put kernel/bpf/syscall.c:1812 [inline] > __bpf_prog_put kernel/bpf/syscall.c:1812 [inline] kernel/bpf/syscall.c:1829 > bpf_prog_put+0x8c/0x4f0 kernel/bpf/syscall.c:1829 kernel/bpf/syscall.c:1829 > > Looks to me like the compiler's inlining decision caused syzbot to see > __bpf_prog_put() instead of bpf_prog_put(), but I can't tell if it's > because it got inlined or because of the .constprop.0 suffix... I > guess syzbot skips the [inline] entries when deciding which function > to report the bug in? Not sure if you are still interested in this or not... But, yes, it's inline frames that are a problem, ".constprop.0" should be stripped. syzkaller parses non-symbolized kernel output w/o inlined frames to extract the title. This was a very early decision, not sure if it's the right one or not. On the other hand using inline frames can cause attribution to all the common one-liners. Now it's somewhat hard to change b/c if we change it, new crashes will be parsed differently and it will cause a storm of duplicates for already reported bugs. > In any case: > > #syz dup: KASAN: vmalloc-out-of-bounds Read in bpf_prog_put > > Vegard
