Kees, On Fri, Feb 09, 2024 at 04:02:32PM -0800, Kees Cook wrote: > On Sat, Feb 10, 2024 at 01:13:06AM +0300, Vitaly Chikunov wrote: > > On Tue, Feb 14, 2023 at 04:08:39PM -0800, Kees Cook wrote: > > > The kernel is globally removing the ambiguous 0-length and 1-element > > > arrays in favor of flexible arrays, so that we can gain both compile-time > > > and run-time array bounds checking[1]. > > > > > > While struct fealist is defined as a "fake" flexible array (via a > > > 1-element array), it is only used for examination of the first array > > > element. Walking the list is performed separately, so there is no reason > > > to treat the "list" member of struct fealist as anything other than a > > > single entry. Adjust the struct and code to match. > > > > > > Additionally, struct fea uses the "name" member either as a dynamic > > > string, or is manually calculated from the start of the struct. Redefine > > > the member as a flexible array. > > > > > > No machine code output differences are produced after these changes. > > > > > > [1] For lots of details, see both: > > > https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays > > > https://people.kernel.org/kees/bounded-flexible-arrays-in-c > > > > > > Cc: Steve French <sfrench@xxxxxxxxx> > > > Cc: Paulo Alcantara <pc@xxxxxx> > > > Cc: Ronnie Sahlberg <lsahlber@xxxxxxxxxx> > > > Cc: Shyam Prasad N <sprasad@xxxxxxxxxxxxx> > > > Cc: Tom Talpey <tom@xxxxxxxxxx> > > > Cc: linux-cifs@xxxxxxxxxxxxxxx > > > Cc: samba-technical@xxxxxxxxxxxxxxx > > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > > > --- > > > fs/cifs/cifspdu.h | 4 ++-- > > > fs/cifs/cifssmb.c | 16 ++++++++-------- > > > 2 files changed, 10 insertions(+), 10 deletions(-) > > > > > > diff --git a/fs/cifs/cifspdu.h b/fs/cifs/cifspdu.h > > > index 623caece2b10..add73be4902c 100644 > > > --- a/fs/cifs/cifspdu.h > > > +++ b/fs/cifs/cifspdu.h > > > @@ -2583,7 +2583,7 @@ struct fea { > > > unsigned char EA_flags; > > > __u8 name_len; > > > __le16 value_len; > > > - char name[1]; > > > + char name[]; > > > /* optionally followed by value */ > > > } __attribute__((packed)); > > > /* flags for _FEA.fEA */ > > > @@ -2591,7 +2591,7 @@ struct fea { > > > > > > struct fealist { > > > __le32 list_len; > > > - struct fea list[1]; > > > + struct fea list; > > > } __attribute__((packed)); > > > > > > /* used to hold an arbitrary blob of data */ > > > diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c > > > index 60dd4e37030a..7c587157d030 100644 > > > --- a/fs/cifs/cifssmb.c > > > +++ b/fs/cifs/cifssmb.c > > > @@ -5787,7 +5787,7 @@ CIFSSMBQAllEAs(const unsigned int xid, struct cifs_tcon *tcon, > > > > > > /* account for ea list len */ > > > list_len -= 4; > > > - temp_fea = ea_response_data->list; > > > + temp_fea = &ea_response_data->list; > > > temp_ptr = (char *)temp_fea; > > > while (list_len > 0) { > > > unsigned int name_len; > > > @@ -5902,7 +5902,7 @@ CIFSSMBSetEA(const unsigned int xid, struct cifs_tcon *tcon, > > > else > > > name_len = strnlen(ea_name, 255); > > > > > > - count = sizeof(*parm_data) + ea_value_len + name_len; > > > + count = sizeof(*parm_data) + 1 + ea_value_len + name_len; > > > pSMB->MaxParameterCount = cpu_to_le16(2); > > > /* BB find max SMB PDU from sess */ > > > pSMB->MaxDataCount = cpu_to_le16(1000); > > > @@ -5926,14 +5926,14 @@ CIFSSMBSetEA(const unsigned int xid, struct cifs_tcon *tcon, > > > byte_count = 3 /* pad */ + params + count; > > > pSMB->DataCount = cpu_to_le16(count); > > > parm_data->list_len = cpu_to_le32(count); > > > - parm_data->list[0].EA_flags = 0; > > > + parm_data->list.EA_flags = 0; > > > /* we checked above that name len is less than 255 */ > > > - parm_data->list[0].name_len = (__u8)name_len; > > > + parm_data->list.name_len = (__u8)name_len; > > > /* EA names are always ASCII */ > > > if (ea_name) > > > - strncpy(parm_data->list[0].name, ea_name, name_len); > > > - parm_data->list[0].name[name_len] = 0; > > > - parm_data->list[0].value_len = cpu_to_le16(ea_value_len); > > > + strncpy(parm_data->list.name, ea_name, name_len); > > > > Could non-applying this patch cause false-positive fortify_panic? > > We got a bug report from user of 6.1.73: > > > > Jan 24 15:15:20 kalt2test.dpt.local kernel: detected buffer overflow in strncpy > > Yes, this seems likely. I would backport this change. > > > Jan 24 15:15:20 kalt2test.dpt.local kernel: ------------[ cut here ]------------ > > Jan 24 15:15:20 kalt2test.dpt.local kernel: kernel BUG at lib/string_helpers.c:1027! > > ... > > Jan 24 15:15:20 kalt2test.dpt.local kernel: Call Trace: > > Jan 24 15:15:20 kalt2test.dpt.local kernel: CIFSSMBSetEA.cold+0xc/0x18 [cifs] > > Jan 24 15:15:20 kalt2test.dpt.local kernel: cifs_xattr_set+0x596/0x690 [cifs] > > Jan 24 15:15:20 kalt2test.dpt.local kernel: __vfs_removexattr+0x52/0x70 > > Jan 24 15:15:20 kalt2test.dpt.local kernel: __vfs_removexattr_locked+0xbc/0x150 > > Jan 24 15:15:20 kalt2test.dpt.local kernel: vfs_removexattr+0x56/0x100 > > Jan 24 15:15:20 kalt2test.dpt.local kernel: removexattr+0x58/0x90 > > Jan 24 15:15:20 kalt2test.dpt.local kernel: __ia32_sys_fremovexattr+0x80/0xa0 > > Jan 24 15:15:20 kalt2test.dpt.local kernel: int80_emulation+0xa9/0x110 > > Jan 24 15:15:20 kalt2test.dpt.local kernel: asm_int80_emulation+0x16/0x20 > > This appears to be a compat call? Likely. This is caused through Wine. Thanks, > > -Kees > > > > > I don't find this patch appled to stable/linux-6.1.y. > > > > Thanks, > > > > ps. (Unfortunately `CIFSSMBSetEA+0xc` address is not resolvable to the > > actual line inside of CIFSSMBSetEA pointing just to the head of it. > > > > (gdb) l *CIFSSMBSetEA+0xc > > 0x6de3c is in CIFSSMBSetEA (fs/smb/client/cifssmb.c:5776). > > 5771 int > > 5772 CIFSSMBSetEA(const unsigned int xid, struct cifs_tcon *tcon, > > 5773 const char *fileName, const char *ea_name, const void *ea_value, > > 5774 const __u16 ea_value_len, const struct nls_table *nls_codepage, > > 5775 struct cifs_sb_info *cifs_sb) > > 5776 { > > 5777 struct smb_com_transaction2_spi_req *pSMB = NULL; > > 5778 struct smb_com_transaction2_spi_rsp *pSMBr = NULL; > > 5779 struct fealist *parm_data; > > 5780 int name_len; > > > > But there is only one strncpy there. > > > > > + parm_data->list.name[name_len] = '\0'; > > > + parm_data->list.value_len = cpu_to_le16(ea_value_len); > > > /* caller ensures that ea_value_len is less than 64K but > > > we need to ensure that it fits within the smb */ > > > > > > @@ -5941,7 +5941,7 @@ CIFSSMBSetEA(const unsigned int xid, struct cifs_tcon *tcon, > > > negotiated SMB buffer size BB */ > > > /* if (ea_value_len > buffer_size - 512 (enough for header)) */ > > > if (ea_value_len) > > > - memcpy(parm_data->list[0].name+name_len+1, > > > + memcpy(parm_data->list.name + name_len + 1, > > > ea_value, ea_value_len); > > > > > > pSMB->TotalDataCount = pSMB->DataCount; > > > -- > > > 2.34.1 > > > > > -- > Kees Cook
