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Howlett" , maple-tree@lists.infradead.org, Vernon Yang From: Marek Szyprowski In-Reply-To: <17b6fc3edc46c4b33aa93b9ef17a63a3a76f4b5f.1679431180.git.lstoakes@gmail.com> Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrPKsWRmVeSWpSXmKPExsWy7djP87r7WmVSDHqOyVrMWb+GzeLr+l/M FtsbHrBbXN41h83i3pr/rBZ3vs1jt9iwsoHJYnZjH6PF3ts32Cx+/5jD5sDlsXPWXXaPzSu0 PDZ9msTucWLGbxaPzUvqPT4+vcXi8X7fVTaPMwuOsHt83iQXwBnFZZOSmpNZllqkb5fAldGz 7BdrwW+Vik8PvrE3ME6R7WLk5JAQMJHYsn8jexcjF4eQwApGiWOHGpggnC+MEpcafjNCOJ8Z JXYs/cTSxcgB1vKigQ0ivpxRYuX/o1AdHxklOmY1s4HM5RWwkzh2cx4riM0ioCqx5e0XVoi4 oMTJmU9YQGxRgRSJiTM2MIEMFRaIkpg3wx0kzCwgLnHryXywmSIC7YwSc5Z1MIM4zALPGSW+ Ny5gBKliEzCU6HrbBbaMUyBSYtr/kywQ3fISzVtngzVICPRzSkzeOIEZ4mwXiWu/6iCeFpZ4 dXwLO4QtI/F/J8Q2CZBtC37fh3ImMEo0PL/FCFFlLXHn3C82kEHMApoS63fpQ4QdJWa072aH mM8nceOtIMQNfBKTtk2HWssr0dEmBFGtJjHr+Dq4tQcvXGKewKg0CylYZiH5fxaSb2Yh7F3A yLKKUTy1tDg3PbXYMC+1XK84Mbe4NC9dLzk/dxMjMI2d/nf80w7Gua8+6h1iZOJgPMQowcGs JMLrxiyRIsSbklhZlVqUH19UmpNafIhRmoNFSZxX2/ZkspBAemJJanZqakFqEUyWiYNTqoEp 7uqHu5wJUhqnohieuv+9Ee+lMdncyLD4RodBwrPNcTO++obUdtSHPZNgmLZx58qru400Vr1Y fbPB5HvCtS2elyxT38tZvdp1IaN1Wccmsd+xtx/JT9TSumopsXPJxkSdXUx3Hh3PjqqLfBtb GycYp2wRXq+n/S3MyleuX/ypVvL/qFXL08I0RDcZK8z2LAm++2CR82IXvU0BRYd3mrMJyvzZ L+KWq7am9T5TcGYUd/mBSdvXdxWwHY31Ebs2N/fd3zvTeAIf5HQqn5RfmL5yrQDnBMeNiwT3 cXMUz52t+EB3xdfi9wZH5/sdXT1nucbTNxO43b/OMJ6x/8RV7gtr9GzMhRUlU5vr9xp/4g1V YinOSDTUYi4qTgQA8xHO0dIDAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrAIsWRmVeSWpSXmKPExsVy+t/xe7r7WmVSDNbc5bOYs34Nm8XX9b+Y LbY3PGC3uLxrDpvFvTX/WS3ufJvHbrFhZQOTxezGPkaLvbdvsFn8/jGHzYHLY+esu+wem1do eWz6NInd48SM3ywem5fUe3x8eovF4/2+q2weZxYcYff4vEkugDNKz6Yov7QkVSEjv7jEVina 0MJIz9DSQs/IxFLP0Ng81srIVEnfziYlNSezLLVI3y5BL6Nn2S/Wgt8qFZ8efGNvYJwi28XI wSEhYCLxooGti5GTQ0hgKaPEmaMFILaEgIzEyWkNrBC2sMSfa11ANVxANe8ZJU6sb2cGSfAK 2EkcuzkPrIhFQFViy9svrBBxQYmTM5+wgNiiAikSE5deZgPZJSwQJTFvhjtImFlAXOLWk/lM IDNFBNoZJZY9O8UGkXjOKPFmJTvEshZGifdPZjGBJNgEDCW63naBFXEKREpM+3+SBaLBTKJr axcjhC0v0bx1NvMERqFZSO6YhWThLCQts5C0LGBkWcUoklpanJueW2yoV5yYW1yal66XnJ+7 iREYtduO/dy8g3Heq496hxiZOBgPMUpwMCuJ8LoxS6QI8aYkVlalFuXHF5XmpBYfYjQFBsZE ZinR5Hxg2sgriTc0MzA1NDGzNDC1NDNWEuf1LOhIFBJITyxJzU5NLUgtgulj4uCUamA6xsHW ZbXZgbWyT4v98ZUNs1sWFcYriTN1uh/fLfjc40dIQfEjgwwv3nVSdpELrz1WWPYs78fmL9fj RT0fTf0YJHY76ei+/RF1urue1a91582543f9WaRyxMQddhyhXR/2Js320XnZu6/ddPWeH9Od xDI0Ny7wr0+ukcsJLVauWfPvxEttXyOjhy+YnjAt8mKOKA//u0CLU8DFpHDNagdr6XPCjgfv s60ve1PQkKOX+eTL3F+n36U3dZ2xuaR0NdzPf4vwnLSZe6Uv33nFf8WkMMa6S+6Yf6F3i15m 7bTXK1oehYu6cnC+fThhvr22cFDpnBXzFQX8tEUOdHv9X/jT2qPBs+xWAd8JjrKPqkosxRmJ hlrMRcWJAIjFDMNjAwAA X-CMS-MailID: 20230323170046eucas1p2483ab0fcc3d6bc56d4b6d09143bbadda X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20230323170046eucas1p2483ab0fcc3d6bc56d4b6d09143bbadda X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20230323170046eucas1p2483ab0fcc3d6bc56d4b6d09143bbadda References: <17b6fc3edc46c4b33aa93b9ef17a63a3a76f4b5f.1679431180.git.lstoakes@gmail.com> X-Rspamd-Queue-Id: 79BAF8002E X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: hhkoa6zakh1hb4811r6rxyjo9tprg7yd X-HE-Tag: 1679590848-385756 X-HE-Meta: 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 iyjm36sf mvlLRUsYpEY7PaO89tM5Xq0fvxIcObqnbCK4L0YpsdDYLekg5Vgn+BYpTymnL5jtTZ8Q4pbSIIYORoNGPFzQTyk2ROutBGQyFq4xeiy+c3lW4lN4Bn8BCc/cIayY7SW1Ui3fYnO/nM+uQpkyVAFYhsNronxPDgnjinYJB X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 21.03.2023 21:45, Lorenzo Stoakes wrote: > Previously, vma was an uninitialised variable which was only definitely > assigned as a result of the logic covering all possible input cases - for > it to have remained uninitialised, prev would have to be NULL, and next > would _have_ to be mergeable. > > We now reuse vma to assign curr and next, so to be absolutely explicit, > ensure this variable is _always_ assigned, and while we're at it remove the > redundant assignment of both res and vma (if prev is NULL then we simply > assign to NULL). > > In addition, we absolutely do rely on addr == curr->vm_start should curr > exist, so assert as much. > > Signed-off-by: Lorenzo Stoakes This patch has been merged into today's linux next-20230323 as commit 6426bbcc76be ("mm/mmap/vma_merge: extend invariants, avoid invalid res, vma"). Unfortunately it breaks booting of some ARM 32bit machines, like Samsung Exynos5422-based Odroid XU3 board. This shortened log shows the issue: Run /sbin/init as init process   with arguments:     /sbin/init   with environment:     HOME=/     TERM=linux 8<--- cut here --- Unhandled fault: page domain fault (0x01b) at 0xb6f03010 [b6f03010] *pgd=b5e84835 Internal error: : 1b [#1] PREEMPT SMP ARM Modules linked in: CPU: 2 PID: 1 Comm: init Not tainted 6.3.0-rc1-00296-g6426bbcc76be #6445 Hardware name: Samsung Exynos (Flattened Device Tree) PC is at vma_merge+0xa0/0x728 LR is at vma_merge+0x294/0x728 pc : []    lr : []    psr: a0000013 ... Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none Control: 10c5387d  Table: 4f11406a  DAC: 00000051 ... Process init (pid: 1, stack limit = 0x5219a5c7) Stack: (0xf0835e30 to 0xf0836000) ...  vma_merge from mprotect_fixup+0xc8/0x290  mprotect_fixup from do_mprotect_pkey.constprop.0+0x210/0x338  do_mprotect_pkey.constprop.0 from ret_fast_syscall+0x0/0x1c Exception stack(0xf0835fa8 to 0xf0835ff0) ... ---[ end trace 0000000000000000 ]--- note: init[1] exited with irqs disabled Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b Reverting it on top of linux-next, together with 183b2bced4c9 ("mm/mmap/vma_merge: init cleanup, be explicit about the non-mergeable case"), which depends on this patch, fixes the boot issue. > --- > mm/mmap.c | 19 ++++++++++++++----- > 1 file changed, 14 insertions(+), 5 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 6361baf75601..7aec49c3bc74 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -911,7 +911,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > { > pgoff_t pglen = (end - addr) >> PAGE_SHIFT; > pgoff_t vma_pgoff; > - struct vm_area_struct *curr, *next, *res = NULL; > + struct vm_area_struct *curr, *next, *res; > struct vm_area_struct *vma, *adjust, *remove, *remove2; > int err = -1; > bool merge_prev = false; > @@ -940,14 +940,18 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > /* Is there a VMA next to a hole (case 1 - 3) or prev (4)? */ > next = vma_lookup(mm, end); > > - /* verify some invariant that must be enforced by the caller */ > + /* > + * By default, we return prev. Cases 3, 4, 8 will instead return next > + * and cases 3, 8 will also update vma to point at next. > + */ > + res = vma = prev; > + > + /* Verify some invariant that must be enforced by the caller. */ > VM_WARN_ON(prev && addr <= prev->vm_start); > - VM_WARN_ON(curr && end > curr->vm_end); > + VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); > VM_WARN_ON(addr >= end); > > if (prev) { > - res = prev; > - vma = prev; > vma_start = prev->vm_start; > vma_pgoff = prev->vm_pgoff; > /* Can we merge the predecessor? */ > @@ -958,6 +962,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > vma_prev(vmi); > } > } > + > /* Can we merge the successor? */ > if (next && mpol_equal(policy, vma_policy(next)) && > can_vma_merge_before(next, vm_flags, > @@ -998,6 +1003,10 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, > adj_start = -(prev->vm_end - addr); > err = dup_anon_vma(next, prev); > } else { > + /* > + * Note that cases 3 and 8 are the ONLY ones where prev > + * is permitted to be (but is not necessarily) NULL. > + */ > vma = next; /* case 3 */ > vma_start = addr; > vma_end = next->vm_end; Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland