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Rozycki" , Thomas Bogendoerfer , Greg Kroah-Hartman , Jiri Slaby Cc: Elena Reshetova , David Windsor , Kees Cook , Hans Liljestrand , linux-mips@vger.kernel.org, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org References: Content-Language: en-US, fr-FR Autocrypt: addr=fainelli@broadcom.com; keydata= xsBNBFPAG8ABCAC3EO02urEwipgbUNJ1r6oI2Vr/+uE389lSEShN2PmL3MVnzhViSAtrYxeT M0Txqn1tOWoIc4QUl6Ggqf5KP6FoRkCrgMMTnUAINsINYXK+3OLe7HjP10h2jDRX4Ajs4Ghs JrZOBru6rH0YrgAhr6O5gG7NE1jhly+EsOa2MpwOiXO4DE/YKZGuVe6Bh87WqmILs9KvnNrQ PcycQnYKTVpqE95d4M824M5cuRB6D1GrYovCsjA9uxo22kPdOoQRAu5gBBn3AdtALFyQj9DQ KQuc39/i/Kt6XLZ/RsBc6qLs+p+JnEuPJngTSfWvzGjpx0nkwCMi4yBb+xk7Hki4kEslABEB AAHNKEZsb3JpYW4gRmFpbmVsbGkgPGZhaW5lbGxpQGJyb2FkY29tLmNvbT7CwSQEEAEKAM4X CgABv0jL/n0t8VEFmtDa8j7qERo7AN0gFAAAAAAAFgABa2V5LXVzYWdlLW1hc2tAcGdwLmNv bY4wFIAAAAAAIAAHcHJlZmVycmVkLWVtYWlsLWVuY29kaW5nQHBncC5jb21wZ3BtaW1lCAsJ CAcDAgEKAhkBBReAAAAAGRhsZGFwOi8va2V5cy5icm9hZGNvbS5jb20FGwMAAAADFgIBBR4B AAAABBUICQoWIQTV2SqX55Fc3tfkfGiBMbXEKbxmoAUCZNaBugUJI+Jo+gAKCRCBMbXEKbxm oNb9B/9/GCiZzNiK61IY24a16Cu83Da7ayx8OhpE/LZC7nkUd8Gd5K7lL+yDcC56aFx1EzKp bsug1GFaMsjAPi8QqMHSCly0S4oCaazZZEikCSIidmlxCLKEglcslpqUBQAeC6oArE9xJh7c zpcBgiMRH1ZJpVZZ5xpwnhsIe9RdT7p4BTDcZ2cErc+jUkGg7FApgIDOrV9vjRQ5khF2zKH8 QYDPhpauwl2SHCBRZtVRi9ur5Jy8PnlkhLf1XEf2MsptHJHE+A7twVtJJaFre6gNPQI0y/dh kCTj3bekpjEP//+/qt3bMRWRPle8a4rlyn5MGqN2ewYgCOuGtu0xtxhvIEmYzsBNBFPAG8EB CACsa+9aKnvtPjGAnO1mn1hHKUBxVML2C3HQaDp5iT8Q8A0ab1OS4akj75P8iXYfZOMVA0Lt 65taiFtiPT7pOZ/yc/5WbKhsPE9dwysrvHjHL2gP4q5vZV/RJduwzx8v9KrMZsVZlKbvcvUv gZmjG9gjPSLssTFhJfa7lhUtowFof0fAq3Zy+vsy5OtEe1xs5kiahdPb2DZSegXW7DFg15GF lj+VG9WSRjSUOKk+4PCDdKl8cy0LJs+rW4CzBB2ARsfNGwRfAJHU4Xeki4a3gje1ISEf+TVx qqLQGWqNsZQ6SS7jjELaB/VlTbrsUEGR1XfIn/sqeskSeQwJiFLeQgj3ABEBAAHCwYEEGAEC ASsFAlPAG8IFGwwAAADAXSAEGQEIAAYFAlPAG8EACgkQk2AGqJgvD1UNFQgAlpN5/qGxQARK eUYOkL7KYvZFl3MAnH2VeNTiGFoVzKHOe7LIwmp3eZ6GYvGyoNG8cOKrIPvXDYGdzzfwxVnD SnAE92dv+H05yanSUv/2HBIZa/LhrPmVhXKgD27XhQjOHRg0a7qOvSKx38skBsderAnBZazf Lw9OukSnrxXqW/5pe3mBHTeUkQC8hHUDCngkn95nnLXaBAhKnRfzFqX1iGENYRH3Zgtis7Zv odzZLfWUC6nN8LDyWZmw/U9HPUaYX8qYMP0n039vwh6GFZCqsFCMyOfYrZeS83vkecAwcoVh 8dlHdke0rnZk/VytXtMe1u2uc9dUOr687hA+Z0L5IQAKCRCBMbXEKbxmoLoHCACXeRGHuijO mOkbyOk7x6fkIG1OXcb46kokr2ptDLN0Ky4nQrWp7XBk9ls/9j5W2apKCcTEHONK2312uMUE ryWI9BlqWnawyVL1LtyxLLpwwsXVq5m5sBkSqma2ldqBu2BHXZg6jntF5vzcXkqG3DCJZ2hO ldFPH+czRwe2OOsiY42E/w7NUyaN6b8Hrw1j77+q3QXldOw/bON361EusWHdbhcRwu3WWFiY 2ZslH+Xr69VtYAoMC1xtDxIvZ96ps9ZXpUPJUqHJr8QSrTG1/zioQH7j/4iMJ07MMPeQNkmj 4kGQOdTcsFfDhYLDdCE5dj5WeE6fYRxEQ3up0ArDSP1L In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e On 5/24/26 16:12, Maciej W. Rozycki wrote: > Revert commit 22a33651a56f ("drivers: convert sbd_duart.map_guard from > atomic_t to refcount_t"), which broke perfectly valid code: > > ------------[ cut here ]------------ > WARNING: CPU: 1 PID: 1 at lib/refcount.c:114 sbd_request_port+0x54/0x140 > refcount_t: increment on 0; use-after-free. > CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.11.0-rc2+ #34 > Stack : 0000000014001fe0 0000000000000000 ffffffff80830000 0000000000000000 > ffffffff8127bc7a ffffffff8016fe08 ffffffff808d0000 ffffffff808d0000 > ffffffff807aa828 ffffffff80822337 ffffffff808ce188 a8000001860b0000 > 0000000000000001 0000000000000001 00000000000001c8 ffffffff808a3090 > 00000000000000bb ffffffff801b09d4 a80000018609bb68 ffffffff801231cc > ffffffff812a0000 ffffffff80171388 0000000000001000 ffffffff807aa828 > 0000000000000001 0000000000000001 0000000000000000 0000000000000000 > 0000000000000000 a80000018609bab0 0000000000000000 ffffffff803c47cc > 0000000000000000 0000000000000000 0000000000000000 0000000000000000 > ffffffff807cb648 ffffffff8010bff8 0000000014001fe1 ffffffff803c47cc > ... > Call Trace: > [] show_stack+0x28/0x88 > [] dump_stack+0x8c/0xc0 > [] __warn+0xe0/0x114 > [] warn_slowpath_fmt+0x40/0x50 > [] sbd_request_port+0x54/0x140 > [] sbd_config_port+0x2c/0x68 > ---[ end trace f666d696412caa3e ]--- > > (report at the offending commit) -- sbd_request_port() is called twice > per DUART instance, to reserve a resource holding the control register > block shared between the two channels, so there's no slightest chance > for an overflow. Also this doesn't stop the driver from working and > it's just the reservation that is missing as a result, i.e.: > > 10060100-100601ff : sb1250-duart > 10060200-100602ff : sb1250-duart > > as from the offending change, vs: > > 10060100-100601ff : sb1250-duart > 10060200-100602ff : sb1250-duart > 10060300-100603ff : sb1250-duart > > beforehand, which is surely why the breakage has gone so long unnoticed. > > "If it ain't broke, don't fix it," so just revert the broken commit. > > Fixes: 22a33651a56f ("drivers: convert sbd_duart.map_guard from atomic_t to refcount_t") > Signed-off-by: Maciej W. Rozycki Tested-by: Florian Fainelli -- Florian