On Mon, 2025-08-18 at 22:17 +0800, Chenzhi Yang wrote: > From: Yang Chenzhi <yang.chenzhi@xxxxxxxx> > > hfsplus_bmap_alloc can trigger a crash if a > record offset or length is larger than node_size > > [ 15.264282] BUG: KASAN: slab-out-of-bounds in hfsplus_bmap_alloc+0x887/0x8b0 > [ 15.265192] Read of size 8 at addr ffff8881085ca188 by task test/183 > [ 15.265949] > [ 15.266163] CPU: 0 UID: 0 PID: 183 Comm: test Not tainted 6.17.0-rc2-gc17b750b3ad9 #14 PREEMPT(voluntary) > [ 15.266165] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 > [ 15.266167] Call Trace: > [ 15.266168] <TASK> > [ 15.266169] dump_stack_lvl+0x53/0x70 > [ 15.266173] print_report+0xd0/0x660 > [ 15.266181] kasan_report+0xce/0x100 > [ 15.266185] hfsplus_bmap_alloc+0x887/0x8b0 > [ 15.266208] hfs_btree_inc_height.isra.0+0xd5/0x7c0 > [ 15.266217] hfsplus_brec_insert+0x870/0xb00 > [ 15.266222] __hfsplus_ext_write_extent+0x428/0x570 > [ 15.266225] __hfsplus_ext_cache_extent+0x5e/0x910 > [ 15.266227] hfsplus_ext_read_extent+0x1b2/0x200 > [ 15.266233] hfsplus_file_extend+0x5a7/0x1000 > [ 15.266237] hfsplus_get_block+0x12b/0x8c0 > [ 15.266238] __block_write_begin_int+0x36b/0x12c0 > [ 15.266251] block_write_begin+0x77/0x110 > [ 15.266252] cont_write_begin+0x428/0x720 > [ 15.266259] hfsplus_write_begin+0x51/0x100 > [ 15.266262] cont_write_begin+0x272/0x720 > [ 15.266270] hfsplus_write_begin+0x51/0x100 > [ 15.266274] generic_perform_write+0x321/0x750 > [ 15.266285] generic_file_write_iter+0xc3/0x310 > [ 15.266289] __kernel_write_iter+0x2fd/0x800 > [ 15.266296] dump_user_range+0x2ea/0x910 > [ 15.266301] elf_core_dump+0x2a94/0x2ed0 > [ 15.266320] vfs_coredump+0x1d85/0x45e0 > [ 15.266349] get_signal+0x12e3/0x1990 > [ 15.266357] arch_do_signal_or_restart+0x89/0x580 > [ 15.266362] irqentry_exit_to_user_mode+0xab/0x110 > [ 15.266364] asm_exc_page_fault+0x26/0x30 > [ 15.266366] RIP: 0033:0x41bd35 > [ 15.266367] Code: bc d1 f3 0f 7f 27 f3 0f 7f 6f 10 f3 0f 7f 77 20 f3 0f 7f 7f 30 49 83 c0 0f 49 29 d0 48 8d 7c 17 31 e9 9f 0b 00 00 66 0f ef c0 <f3> 0f 6f 0e f3 0f 6f 56 10 66 0f 74 c1 66 0f d7 d0 49 83 f8f > [ 15.266369] RSP: 002b:00007ffc9e62d078 EFLAGS: 00010283 > [ 15.266371] RAX: 00007ffc9e62d100 RBX: 0000000000000000 RCX: 0000000000000000 > [ 15.266372] RDX: 00000000000000e0 RSI: 0000000000000000 RDI: 00007ffc9e62d100 > [ 15.266373] RBP: 0000400000000040 R08: 00000000000000e0 R09: 0000000000000000 > [ 15.266374] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > [ 15.266375] R13: 0000000000000000 R14: 0000000000000000 R15: 0000400000000000 > [ 15.266376] </TASK> > > When calling hfsplus_bmap_alloc to allocate a free node, this function > first retrieves the bitmap from header node and map node using node->page > together with the offset and length from hfs_brec_lenoff > > ``` > len = hfs_brec_lenoff(node, 2, &off16); > off = off16; > > off += node->page_offset; > pagep = node->page + (off >> PAGE_SHIFT); > data = kmap_local_page(*pagep); > ``` > > However, if the retrieved offset or length is invalid(i.e. exceeds > node_size), the code may end up accessing pages outside the allocated > range for this node. > > This patch adds proper validation of both offset and length before use, > preventing out-of-bounds page access. Move is_bnode_offset_valid and > check_and_correct_requested_length to hfsplus_fs.h, as they may be > required by other functions. > > Reported-by: syzbot+356aed408415a56543cd@xxxxxxxxxxxxxxxxxxxxxxxxx > Closes: https://lore.kernel.org/all/67bcb4a6.050a0220.bbfd1.008f.GAE@xxxxxxxxxx/ > Signed-off-by: Yang Chenzhi <yang.chenzhi@xxxxxxxx> > --- > fs/hfsplus/bnode.c | 41 ---------------------------------------- > fs/hfsplus/btree.c | 6 ++++++ > fs/hfsplus/hfsplus_fs.h | 42 +++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 48 insertions(+), 41 deletions(-) > > diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c > index 14f4995588ff..407d5152eb41 100644 > --- a/fs/hfsplus/bnode.c > +++ b/fs/hfsplus/bnode.c > @@ -18,47 +18,6 @@ > #include "hfsplus_fs.h" > #include "hfsplus_raw.h" > > -static inline > -bool is_bnode_offset_valid(struct hfs_bnode *node, int off) > -{ > - bool is_valid = off < node->tree->node_size; > - > - if (!is_valid) { > - pr_err("requested invalid offset: " > - "NODE: id %u, type %#x, height %u, " > - "node_size %u, offset %d\n", > - node->this, node->type, node->height, > - node->tree->node_size, off); > - } > - > - return is_valid; > -} > - > -static inline > -int check_and_correct_requested_length(struct hfs_bnode *node, int off, int len) > -{ > - unsigned int node_size; > - > - if (!is_bnode_offset_valid(node, off)) > - return 0; > - > - node_size = node->tree->node_size; > - > - if ((off + len) > node_size) { > - int new_len = (int)node_size - off; > - > - pr_err("requested length has been corrected: " > - "NODE: id %u, type %#x, height %u, " > - "node_size %u, offset %d, " > - "requested_len %d, corrected_len %d\n", > - node->this, node->type, node->height, > - node->tree->node_size, off, len, new_len); > - > - return new_len; > - } > - > - return len; > -} > > /* Copy a specified range of bytes from the raw data of a node */ > void hfs_bnode_read(struct hfs_bnode *node, void *buf, int off, int len) > diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c > index 9e1732a2b92a..fe6a54c4083c 100644 > --- a/fs/hfsplus/btree.c > +++ b/fs/hfsplus/btree.c > @@ -393,6 +393,12 @@ struct hfs_bnode *hfs_bmap_alloc(struct hfs_btree *tree) > len = hfs_brec_lenoff(node, 2, &off16); > off = off16; > > + if (!is_bnode_offset_valid(node, off)) { > + hfs_bnode_put(node); > + return ERR_PTR(-EIO); > + } > + len = check_and_correct_requested_length(node, off, len); > + > off += node->page_offset; > pagep = node->page + (off >> PAGE_SHIFT); > data = kmap_local_page(*pagep); > diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h > index 96a5c24813dd..49965cd45261 100644 > --- a/fs/hfsplus/hfsplus_fs.h > +++ b/fs/hfsplus/hfsplus_fs.h > @@ -577,6 +577,48 @@ hfsplus_btree_lock_class(struct hfs_btree *tree) > return class; > } > > +static inline > +bool is_bnode_offset_valid(struct hfs_bnode *node, int off) > +{ > + bool is_valid = off < node->tree->node_size; > + > + if (!is_valid) { > + pr_err("requested invalid offset: " > + "NODE: id %u, type %#x, height %u, " > + "node_size %u, offset %d\n", > + node->this, node->type, node->height, > + node->tree->node_size, off); > + } > + > + return is_valid; > +} > + > +static inline > +int check_and_correct_requested_length(struct hfs_bnode *node, int off, int len) > +{ > + unsigned int node_size; > + > + if (!is_bnode_offset_valid(node, off)) > + return 0; > + > + node_size = node->tree->node_size; > + > + if ((off + len) > node_size) { > + int new_len = (int)node_size - off; > + > + pr_err("requested length has been corrected: " > + "NODE: id %u, type %#x, height %u, " > + "node_size %u, offset %d, " > + "requested_len %d, corrected_len %d\n", > + node->this, node->type, node->height, > + node->tree->node_size, off, len, new_len); > + > + return new_len; > + } > + > + return len; > +} > + > /* compatibility */ > #define hfsp_mt2ut(t) (struct timespec64){ .tv_sec = __hfsp_mt2ut(t) } > #define hfsp_ut2mt(t) __hfsp_ut2mt((t).tv_sec) Looks good. Reviewed-by: Viacheslav Dubeyko <slava@xxxxxxxxxxx> Thanks, Slava.
