[resent with akpm's proper email address (either me or my mailer did something stupid; sorry for the noise)] On 11.01.23 11:46, Linux kernel regression tracking (Thorsten Leemhuis) wrote: > Hi, I noticed a regression report in bugzilla.kernel.org. As many > (most?) kernel developer don't keep an eye on it, I decided to forward > it by mail. Quoting from > https://bugzilla.kernel.org/show_bug.cgi?id=216911 : > >> Amanieu d'Antras 2023-01-11 02:10:02 UTC >> >> Created attachment 303572 [details] >> Program which demonstrates this issue >> >> The vm_unmapped_area function doesn't seem to respect info.low_limit and will sometimes return an address below this limit. This can result in addresses below mmap_min_addr being returned. >> >> I bisected it down to this range of commits (I stopped since I was hitting kernel crashes): >> 3499a13168da mm/mmap: use maple tree for unmapped_area{_topdown} >> 7fdbd37da5c6 mm/mmap: use the maple tree for find_vma_prev() instead of the rbtree >> be8432e7166e mm/mmap: use the maple tree in find_vma() instead of the rbtree. >> 2e3af1db1744 mmap: use the VMA iterator in count_vma_pages_range() >> f39af05949a4 mm: add VMA iterator >> d4af56c5c7c6 mm: start tracking VMAs with maple tree > > [those are all from the Maple Tree introduction series] > >> I've attached a test program which attempts to allocate the entire address space. On affected kernels, this triggers one of the 2 assertions (depending on whether you are running as root): >> - NULL is returned, which means memory below mmap_min_addr was allocated. >> - EPERM is returned, which really shouldn't happen when MAP_FIXED is not used (ENOMEM should be returned instead). > > See the ticket for more details. > > BTW, let me use this mail to also add the report to the list of tracked > regressions to ensure it's doesn't fall through the cracks: > > #regzbot introduced: d4af56c5c7c6..3499a13168da > https://bugzilla.kernel.org/show_bug.cgi?id=216911 > #regzbot title: mm: get_unmapped_area returns addresses below mmap_min_addr > #regzbot ignore-activity > > Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat) > -- > Everything you wanna know about Linux kernel regression tracking: > https://linux-regtracking.leemhuis.info/about/#tldr > If I did something stupid, please tell me, as explained on that page.
